More than 30 definitely. Hundreds if you count every account ever from when I first got internet access to now.
I don't think anyone who has had internet access for more than a month can have less than 30 accounts created total, so this has to be about actively used accounts.
15-20-ish actively used.
Though facebook, twitter and all similar social networking shenanigans I avoid like the plague.
Don't understand why anyone would ever use such a site, but that's their problem (Not worth starting an argument over).