Lindsay Lohan sure does know how to pick 'em!

Her rehab rendevous Riley Giles is stabbing her in the back!  After Lindsay kicked him to the curb, Riley has decided to cash in on his short relationship with Lohan.

Giles told the News of the World that Lindsay "quit coke and got hooked on sex with me."

As if calling Lindsay a sex addict isn't enough, Riley is also trying to sell some risque photos of Lohan evidently taken by Giles while they were dating.

Lohan and Giles broke off their relationship shortly after Thanksgiving. Since then, Lohan has been spotted out with 24-year-old Spencer Guilbert.