That's funny, the exact same thing has been happening recently with some of my friends, two of them in particular. I think it is such a childish thing to be doing. We still get along alright, but I've started to cut things off with them and spend more time with my friends who include me and act like they actually want me there. This may sound harsh, but if your "friends" are treating you that way, they're not the type of friends you want to keep.