People using people
I liked it, especially the ending, how Kutcher's character comes back to Heche's home to give them some pizza. She already has a new "boyfriend", some hot guy who is mainly interested in her only because she's giving him the high life. That leads me to believe that she was using him as much as he was using her. No woman in the world is going to fall for Kutcher's cheap tricks and twenty-six point strategy... unless she wants to fall for it on purpose, thinking "why not? let's enjoy him while he lasts!"
Even more, Heather tried to use Nikki, but she failed because he was not rich. But Samantha really used Nikki: she put up with him until she got tired of him. Good for her!