It’s not an easy fix. You need various plugins to block spam but as stated above people are earning pennies to sign up to blogs. Best defense is a strong offense. Do as much as you can. Spam is a fact of life when running social sites.
Install my BuddyPress verified plugin and you can easily manage your spam accounts. I’m adding a feature in the next update that will deactivate an account automatically if that account posts too much if they are too new.
Core BP committer Paul is adding askimet filtering to the activity stream. Everyone knows spam is an issue and it’s being dealt with as best it can.
