Jason Kottke says this video of a man walking on hot lava "might be the dumbest thing on YouTube, which is saying quite a lot."
And that does seem pretty dumb. Over at Wired, however, volcano blogger Erik Klemetti explains that it's technically possible to walk on some types of lava. It's probably not a great idea, though:
[I]f that flow has a decent crust (which it does) and is moving fairly slow (which it is), and if you move quickly, your weight isn’t going to be enough to cause you to sink into the flow.
The big caveat here is that if the crust is uneven and you hit a thinner part, you could find yourself with more lava on your boot that you’d like (that is, more than “no lava”) or worse, trip and stick your hand on the flow surface that is still likely very hot when you fall.
He adds this caveat:
This isn’t to say you should ever do what this guy did. Don’t. There are many things you could do and survive but shouldn’t because there are very high probabilities that you’ll get hurt.
So there you go: Walking on hot lava, not the world's greatest idea.