Justin Kan (just Google him--I'm uncomfortable providing a link) is wearing a wireless, head-mounted camera and streaming the feed to the Web. He has promised to do this constantly with the exception of times when he's talking business. His is explicitly a commercial venture: He hopes to attract enough advertising that he can turn a profit and perhaps recruit a whole stable of "lifebloggers."
Justin's venture is the logical extension of blogs and will probably become more common as bandwidth and cameras fall in price. (In fact, Natalie Portman of Star Wars fame is apparently in talks to launch a feed that would be all Natalie, all the time.)
Popular lifebloggers might attract significant fan bases and would certainly compete with one another. We can expect to see steadily more outrageous behavior--lifebloggers putting themselves into ever weirder, ever more dangerous situations. Travel is also a possibility--tourist destinations would pay lifebloggers to visit and enjoy royal treatment plus fun in the sun. (And if you want royal treatment yourself, you can strap a cheap dummy camera to your head for the duration of your trip.)
Some lifebloggers will be more interesting in the second person than in the first. In other words, it might be much more fun to watch Natalie Portman than to watch what she's watching (what stars look at is probably only a little more interesting than what the rest of us look at, after all). Second person video, of course, requires a crew, which drives costs into Reality TV territory. So it's not clear that stars like Natalie will be able to effectively monetize their...well, their lives, I guess; that's what it comes down to.
Justin.TV is nauseating, by the way. Not because of his life (which seems to be about as dull as mine) but because of the way the camera rolls around. I'm assuming this is a technical problem that can be overcome with better image stabilization, but maybe it's intrinsic to head-mounted videocams...in which case the art form will probably come to be known as (good luck attracting advertisers!) DramamineTV. Which may not actually be a barrier to success. Conventional TV frequently induces stomach upset, and it seems to survive just fine.