WAIT!! NOT recommended. AT ALL.
Go fluffyfeathers - have fun. That's not an issue.
But if you're thinking about tanking lower levels for faster queues, please consider healing instead. You'll save both your fist and your monitor some injury through frustration. (And some gold, since you REALLY need to be on top of the gear for your level to tank and not get 2 shot as Bear.) My lowbie bear made it to 48 or so (Dire Maul specifically was when I killed her bear spec), before giving up. She just died way too often and every healer I spoke to had the same story (before booting her): "It's just how bears are at lower levels." In approximately equal, if not lesser, healing gear she was fine.
I've actually never tried healing, but I bet I'd love it.
Thanks for the advice. I wish I could dual spec this low, but I think I'll try resto for a little while and see what I think. I've played with bear form a bit, and although I enjoy tanking, it wasn't that great for me.