This kind of deal is definitely becoming more popular, with mainstream media companies hosting bloggers. I am currently in negotiations for something similar for my own blog, though not with a company as large as Time (darn the luck), and I expect it will probably happen in the next couple weeks. The key thing, of course, is that they have promised no editorial control whatsoever. In fact, they don't want me to change anything from what I'm already doing. I'll likely have an announcement when everything is settled.