Nice look but a HUGE flaw.
You use an e-mail actiavation system to prevent spam users. I or anyone with a small amount of knowledge can create a tiny script that will create millions of fake users.
At the momment you do this;
Sign up page or box -> fill details in -> validate and submit -> send e-mail -> Wait for user to click link in e-mail -> everything works
But the way you do it is really really bad.
For example;
I signed up with email@email.com and managed to active my account with http://www.friendr.co.uk/activateuser.php?email=email@email.com
You need checksums to stop it. If you require a demo then I'll happily help.
All the best
PaulTheProgrammer