the ones I see don't have any useful content, they are just there for the purpose of selling links....
Again, it all depends if you're doing it right. Right now I've purchased 7 domains, paid for resell rights for the script, and bought over 15 backlinks from other clouds and I'm still in the green
Yes...but you're purchasing worthless links that go for $1. Those domains transfer very little value to your blog, which in turn passes even less value to the 7 domains that you purchased. Now with that in mind, there is no way you can maintain the PR from 7 expired domains relying on word cloud links that you purchased.
say no to cloud sites - they are lot's of links in one page and they are not relevant - read more about Cloud Links
I managed to snag a site thats on Million Dollar Homepage for $20. Its PR4 (predicted to go PR5) but mainly because I've busted my hump to get it there. Even though the million dollar homepage is pretty much garbage now, its iconic. And I like that. I just feel sorry for the poor guy that shelled out $900 for the adspace I've got.