Can anyone do it?
No.
It should be possible, technically.
Surely with an insane amount of practice one could balance on a wheel and walk on it, sort of like half log rolling and half unicycling/UWing.
That’s not to say anyone can or has gotten close, but there’s nothing inherently impossible about it.
And now we reach the simpler points of your statement, making it seem possible-er.
in my 3 cents worth, its possible, but it’d be way too hard.
you would need to either be rolling fast enough that the wheel would keep itself standing (gyroscopic), so as it wouldnt tip over sideways, or you’d have to have the wheel perfectly straight. The slightest tipping motion would cause it to fall, its like trying to ballance a 12’’ ruler on another 12’’ ruler that your already balancing, it’d just be really really weird and hard.
Indeed, there would be nearly no margin for error. It would take an incredible amount of core body strength to make the adjustments required to recover from the slightest tilt, and anything more than the slightest would send you toppling over.
Still though it’s possible and if you ask me it’s only a matter of time until some crazy kid spends their whole life learning how to do it.
probably not haha
Think it through.
First big problem: When wheel walking on a uni, your balance is derived to a great extent from your weight on the seat, and your crotch holding the wheel via the fork. In essence, WW a UW means there is no such source of balance, making it possibly impossible.
Second big problem: Even when riding a UW conventionally, using the pedals, the UW goes from side to side against the rider’s calves. Crazy side to side motion appears to be intrinsic to the UW. With no calves to limit the side to side motion, the UW will go down flat sideways to the ground, making it possibly impossible.
Third big problem: When wheel walking on a uni, your weight is on the seat so you’re not STANDING on the wheel, like you’d do with UW WWg. This helps in those moments when switching from one foot to the other. The light touch also allows for speed control. The heavy touch of WW on a UW means virtually NO speed control. As soon as your foot rolls the UW forward a bit, that foot is VERY RAPIDLY carried down to the ground, ending the WW, making it possibly impossible.
I’m one to encourage and fill with hope, so I’m not saying it’s impossible.
But think it through: It’s going to be mighty difficult.
Billy
First big problem: When wheel walking on a uni, your balance is derived to a great extent from your weight on the seat, and your crotch holding the wheel via the fork. In essence, WW a UW means there is no such source of balance, making it possibly impossible.
It makes it different and probably harder, that’s all.
Second big problem: Even when riding a UW conventionally, using the pedals, the UW goes from side to side against the rider’s calves. Crazy side to side motion appears to be intrinsic to the UW. With no calves to limit the side to side motion, the UW will go down flat sideways to the ground, making it possibly impossible.
The side to side motion is not intrinsic to the wheel. This motion is a result of you exerting a force on the pedals. You must push slightly more on the pedal going down than the pedal going up (if going forward, otherwise you wouldn’t go anywhere). This results in the wheel going side to side. If you were standing on top of the wheel this would not happen because you would only be pushing down towards the ground, through the point of contact between the wheel and the ground. In this scenario it would not shift side to side.
Third big problem: When wheel walking on a uni, your weight is on the seat so you’re not STANDING on the wheel, like you’d do with UW WWg. This helps in those moments when switching from one foot to the other. The light touch also allows for speed control. The heavy touch of WW on a UW means virtually NO speed control. As soon as your foot rolls the UW forward a bit, that foot is VERY RAPIDLY carried down to the ground, ending the WW, making it possibly impossible.
The heavy touch means you need to balance yourself properly. In this case balance is more involved. Just like log rolling, you still have speed control, but it’s a lot harder. You would have to be very mindful of where you’re balancing, both side to side and front to back.
Yeah, the things you’ve listed make it an incredible challenge, but they don’t make it impossible. It would be very different from unicycle WWing. I have thought it through and I recognize how retardedly hard it would be, but that is not to say that it is impossible and that nobody would ever be able to do it.
just make a UW out of a car tire… problems solved…
If it is ever done it will be with a wide wide tire that has been squared off by sanding the tread profile square or other means. The extreme would be using a wide car tire.
You said it! ^^
I was trying to edit my last message with the following before you posted too!
http://www.youtube.com/watch?v=1AYtEK_6pNA
While it’s very different because it’s heavy and you don’t have to balance left to right (only forward/back), and this guy is doing it sideways, it’s possible.
Trying and failing:
http://www.youtube.com/watch?v=zejPGaTCxX4
Another one:
http://www.youtube.com/watch?v=0d2LJo2FO9E
I still think it’s possible, although insanely difficult. Although, it’s quite unrelated to unicycle WWing.
No-one even thougth about transitions riding to ww or other way around 
It’s gonna be so cool:p
Just try the tire walkin like above, then switch to thinner tires and so on. you’ll develop the balance
Its possible but its a stupid and pointless thing to spend mass quantities of time practicing. I mean I could spend all of my life counting grains of sand on a beach but it would be a massive time waster.
Unlike super-sensible activities like unicycling, seatwraps and crankflips, all guaranteed to bring about world peace in the blink of an eye?
I would envisage an easy ‘starter-way’ to get going on WW the ultimate wheel would be to walk on the sides of the rim at the bottom.
That was you’d still have the top of the wheel to brace against the calves.
A bit of a ‘cheat’ I know, but it might be a start.
Don’t forget stand up or seat out wheel walking. Problems one and three are mostly solved there. Somebody good at wheel wlaking hardly wobbles at all so two isn’t a big issue either.
It’ll still be very hard though
I used to be able to idle with one foot on the pedal and the other on the wheel. I admit that is a much easier trick but I have virtually no freestyle skill at all.
I think the closest to this trick is the backward ww seat in front (not touching the body, with the arms extended) that Julien Money does (e.g. in the K1 freestyle roadtrip).
This is probably the only ww trick where most of your weight rests on the wheel. It is also really hard (at least it took me a long time to learn it). The biggest problem is indeed that the smallest inaccuracy in foot placement will tilt the wheel to one side. To some extend you can compensate this via your arms holding the saddle, but you just can’t exert much force. Without that help it seems close to impossible. Note that you normally also steer the wheel, if only to keep your sideways balance. Without holding the seat that must be incredibly hard.
Still it might be possible 
Maybe you could start by doing a stillstand standing with one foot one the wheel…
Does anyone do this with a seat drag??
That’s closer to what we’re talking about here.
A tire, 2 pedals, and BAM. You’ve got yourself one lean, mean, wheel walkin’ machine
I tried walking on it, but didnt’ get very far. Perhaps one revolution at most. But still, I did it! haha
Show the video!!!
I can walk on a car tire, but havent tried anything smaller.