What is with guys touching the butt?

Because they like you butt.

It's probably more acceptable and less likely to draw a slap in the face than grabbing elsewhere, so they do what they can get away with. I think the thong has a lot to do with it. At one time showing cheeks on the beach was taboo. Now they are all out there in the tabloids and movies. It's not considered off limits like it once was, so the response has changed as well. Plus the thong tends to change the way your street cloths fit by accentuating your contours. More temptation all around. If you don't care for it, remember not to go to Italy.

omg I'm in that same position, just my friends make fun of my butt ,and say you have a bigg ass
kinda depressing O.o

They just do that because you let them get away with it. In my opinion, that's pretty disrespectful. Even if you do have a big butt that doesn't mean they have the right to touch you. But if you're OK with that, then that's you.

Well first off, be careful not to give your guy friends the wrong idea by letting them all touch your butt. Guys like butts and if a girl lets them touch then they're all about it. As for the girls that say you don't have a butt, that's probably their way of telling you you're not fat. You know how we females ask questions that are like double edged swords lol. It's hard for people to interepret whether we're doing that or not, so they give the safest answer possible.