What effects does spending a lot of time in online communities have on interpersonal skills?
There seems to be a difference between social community users and non-users (e.g. http://dx.doi.org/10.1016/j.chb.2013.01.026), but these are only correlative data, not causative, but in a recent study "Facebook usage was found to interact with measures of psychological well-being, suggesting that it might be beneficial to students experiencing low self-esteem and low life satisfaction." (http://dx.doi.org/10.1080/0144929X.2010.550063)

This is just a quick hint and doesn't comprehensively answer your question, but maybe the articles contain references to other research.

Follow the links to get to the original publications and a short abstract describing the study and results.



More stuff I found through a Google Scholar search for "online communities effects":

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC411092/
http://repository.maestra.net/valutazione/MaterialeSarti/articoli/Johnson-Survey.pdf
etc.

I don't know, if any of this is relevant, I just want to give you ideas to do your own research.

If you access Google Scholar through a university network, you'll get links to most of the articles, otherwise you'll still be able to read most of the abstracts.