Research on online friendships

[tmuwra]

Hi, I'm conducting some research into how well the friends we have in different contexts really know us.  In particular whether our online friends know us better than our offline friends or the other way around.  I need participants with online friends to participate by completing an online personality survey and then invite an online friend and an offline friend to also complete some questions about them.   It's all completely confidential and anonymous, but I'm having trouble finding participants in the first place, and in persuading participants to ask their friends to get involved too.

So I'd be grateful for some advice on how to persuade more people to participate and to ask their friends to answer questions about them.  I've put in lots of reassurances about confidentiality and privacy and not making people open to spam etc, but is there anything else I can do?

Thanks!