I've been thinking a lot about this question recently, but not as much from a friendship angle as from an instruction angle. I've begun to question the efficacy of subject/grade acceleration when it just means sending a gifted child to class with older children for more advanced content. While it is certainly better than being in class without acceleration, it seems to presume that gifted children can have their needs met through a change in "what" rather than a change in "how", kwim? This assumes that the differences are based only on level of attainment, and not on differences in how the learning has to occur.