Yeah, a game like Guild Wars wouldn't be one you could rent. Like Shini said, the Access Key comes with the disc, so if they rent the disc either A. It would be banned because of how many people are logging in with it, or B. Everyone would be able to steal your characters because it all uses the same access key.
I'll admit, most of what I'm seeing I'm not very impressed with, although that Sin pic you just put there looks pretty cool. Although, at this point I have to say nothing I'm seeing to catching my interest enough for me to consider getting it, sorry. I'm probably just too much of a loner, I don't like the idea of an online game where you almost have to hunt with people when you play (that includes Henchmen), I like it better when you can hunt alone if you feel like it, and then when your in the mood for a group hunt you can gather some people up. I don't like the idea of always having the depend on others when you log-in (again, that includes Henchmen, because from what I understand they're even ALLOT less dependable than actual PCs).
Still, it looks like a good game if you're not such a chronic loner like me, lol.