"Friends with benefits" relationships never fulfill for their intended purpose: getting one's rocks off without any emotional commitment or attachment. At least in movies they don't. Why? Because both parties always let their guard down and live happily ever after. But "happily ever after" ends when you realize you're in a long term relationship that you weren't ready for and, thus, have to go through the pain and humilation of a break-up, not to mention the six months of wallowing and weight gain.

Don't get us wrong—we're still going to check out Mila Kunis and Justin Timberlake work through it in their new rom-com Friends With Benefits (in theaters tomorrow). We just want caution you about the pitfalls of real-life, strictly sexual relationships before Hollywood makes you start irrationally seeing a FWB as anything other than problematic. If you're considering a Kunis/Timberlake-like fling, first consult our following Guide To Surviving A Friends With Benefits Relationship.