Doesn't look authentic to me. There's really only a hand full of authentic full cast signed friends photo's in existence, so they are very rare. Matthew Perry, Matt LeBlanc's and Jennifer Anistons signatures look very different then the ones I got in person from them. I will try to scan those later for you to compare to.
I agree with guilder 1rst. Signatures look totally different than ones I've gotten in person. And remember a good percentage of autographs sold on ebay are fake. Only buy from a reputable dealer to be sure.