If you've never used Badoo, I would encourage you to sign up just to see what tactics they use to encourage users to pay, how they do account retention and also how they encourage you to add profile information and photos. Interesting stuff.
I actually went there, and somehow in 2h I filled in ~80% of my profile data, uploaded some photos and paid for additional features. Not that I was fighting with myself, or something, but those tactics do work. They seem well optimized, attracting one to act without being too annoying.
'There's one message waiting for you!'
And I don't think I will ever try. I'm still pissed at it.