Can Online Games and Virtual Worlds help language learners?

Online Games and Virtual Worlds
Online Games and Virtual worlds become more popular everyday. Some teachers think it may be a good idea to use Second Life as language learning resourse... I still doubt this opportunity. First of all it is some kind of a game that is addictive - students will be more interested in travelling around the virtual world and create a house or open a restaurant than to learn language. Secondly, there are a lot of places that are only for adults... I don't think it is good for kids. Then... adults themselves want to relax in Second Life and do what they don't do in real life. And finally I have just read about Language Teachers' Meeting in Second Life and I may say that it was not an effective one. I do believe that for language leaners it is better to look at http://livemocha.com/ or http://sharedtalk.com/ nin oreder to find friends and talk with them and help them to learn your language as well.