Put me in the "sub-cultures, not subraces" column. I like some cultural variations, but don't need them mechanically distinct in significant ways (ability scores, etc). I'm OK with minor mechanical differences that reflect culture, though -- like different favored weapons, or preferred classes, or the like.
The only ones I'm not certain on are aquatic elves (obviously, they need to be mechanically different to breathe water) and drow (which feel better with some magical differences at least). But I'm almost ready to treat those two variations as completely separate races.
As to number ... I'm fine with an upper limit of Greyhawk varieties: Grey, High, Wood, Wild, Aquatic, Drow (and consider Valley to be a High or Wild Elf culture, not a distinct variety), and probably at least one of those is redundant, possibly two. More than that ... no. Avariel, for example, have always seemed downright silly to me.