Language-Sharing Programs

Has anyone tried out internet sites for language learning, in which users share their knowledge with one another? Let’s say your native language is French and you want to learn Russian; on such a site, you can find someone whose native tongue is Russian and who wants to learn French. You two can work together online, exchanging your knowledge. My university actually has a program like this and recently I’ve heard about Palabea, a site with users from 190 countries. I’ve looked at Palabea, but I am not sure if I think such sites can work so well; just because someone has a particular native language doesn’t mean that s/he knows how to teach the grammar, vocabulary, and pronunciation to another person. I might try it out at some point, anyway, so I’d be glad to hear what experience others have with language-sharing programs.