I've never done any synchro myself, but the rec center rink in my town has a very strong synchro program (many national championships), and they have a boy on one of their teams. There's a fun video here that shows three of the teams in action (including the boy):
I went to synchronized skating national championships in Providence, RI (in 2008, I think) and there at least one team with several men on the team, using them to be able to do lifts (pairs style - one man lifting one female). I went again to the national synchro championship this past year, and there were fewer men - the top teams were all female, (using groups of females to lift one female).
I think it's great when guys do synchro, but given how men/boys are a minority in figure skating in general, I'm not surprised that there are not a lot of them in synchro.