 Framing other sites has always seemed scummy to me.  Am I off-base?
chris11: That's why I've never really liked about.com. Looking into it, it seems like all the content has been paid for by about.com. But content on their sites has appeared elsewhere, and it looks like they frame content, so it's just distasteful.I do think it can be done well though. Isitfunnytoday.com 
frames content. They are a web comic aggregator that lets people vote on web comics. On all their out going links, they have a very small frame that lets you vote on the displayed comic, vote on a different comic, and share the the comic on websites like digg. The bar is not invasive, and you can easily get rid of it by clicking the red x. It also helps that isitfunnytoday.com is actually sending more traffic to the other site.