Sex with friends' sisters. Acceptable?

[wdeadwyler]

I always thought that for a friend to have sex with a good (or best) friend's sister (especially little) was considered a huge transgression, possibly one to terminate a friendship. Recently, a female friend of mine informed me that her sister was breaking up with her boyfriend, and then encouraged me to go for it with her little sister. Furthermore, I have heard stories from my friends about times they have had sex with their friends' sisters and all was fine in the end, one even borrowed a condom from his friend to bang said friend's sister in a closet. My friends have some hot sisters, Im not gonna pretend I havent thought about hitting a few.

What do you guys think. Anyone have any (hopefully hilarious) stories, or just general commentary on such situations?