As pointed out by several posters: Orcs have nature affinity.
I really can't see any reason for humans not being hunters, as well as BElfs not being warriors. I realize that the latter has some trumped up lore behind it (actually not really, just something blizz made up to keep whiners shut up) and they have too much magical affinity to play a class without mana. In reality it's **** and bull. The lore reason is completely made up out of convenience reasons, and just the thought of a gnome being able to play warrior, but a Blood Elf not to... It's pretty retarded. A *********** high, pale, fat little humanoid can swing 2h:ers and main-tank huge raid bosses. Yeah, right.
Truth to be told, they could even work out the racials to make warrior BElfs work. Just have ti drain mana the usual way, and when released silence and give 5 rage per charge. Quite easy, but rumours say that it was between hunters and warriors in the end, and the Legolas freaks won. Curses I say, CURSES!!
As far as balance is concearned, I myself wouldn't think this is an issue. As a matter of fact, it's already un-balanced. Now, I'm not the kinda guy that would sit down a ransack all races and make sure each faction have equal avalability to the classes (but more the kinda guy who'd think classes that are obvious to be avalable to a certain race, and vice versa, is a better way to go about it).
Basicly, I think it's just as obvious that dwarves shouldn't be able to be rogues, as it is taurens shouldn't (infact mages would be a better choice for that race...). Kinda obvious that an under-sized, bald, old fart (the image of my steriotypical gnome...) shouldn't be able to be warrior, or involved with anything related to "rage" (I mean seriously... in addition to their appearance, their +5% int racils should be enough to make blizzard scream OH NO FOR ***** SAKE NOT WARRIORS!!!! But that might just be the bear talking there...). Rather, then, a priest, since they seem to have alot of magical affinity. I really think humans should be able to choose hunter, I really do. But they're already able to be all other classes in the game, so it'd be a pick between rogue -> hunter or warlock -> hunter. Imo, humans not being able to be warlocks would be more likely than them not being able to be hunters.
In the end what I'm trying to say here is:
I despise all gnomes. Particularly the warrior ones. I think they're a mockery to their class.
I don't care about blizzards idea of balance. If people have inadequate lives enough to sit and compare which faction is allowed most classes, that's pretty much their own problem.
I hope they'll raise the class-cap to 8, and that you'll be able to start a Death Knight from level 1.
The best pet is a boar.
North is infact a hairy englishman pretending to be a girl for rateups.
That's about it.