BMC Psychiatry have published a research article on people who use depression virtual communities:

http://www.biomedcentral.com/1471-244X/3/19/abstract

there is a link there to the full text PDF version

the authors say "There are high levels of untreated and undiagnosed depression in users of Internet depression communities. This group represents a target for intervention. Internet communities can provide information and support for stigmatizing conditions that inhibit more traditional modes of information seeking."