What would you do?#107 - When to fold AK?

Full Tilt Poker $0.25/$0.50 No Limit Hold'em - 9 players
The Official DeucesCracked.com Hand History Converter

MP2: $54.55
CO: $62.60
BTN: $54.45
Hero (SB): $61.05
BB: $93.10- 7/4 / 0% 3bet / 0% steal / infinite aggression factor @ 137 hands
UTG: $13.85
UTG+1: $72.40
UTG+2: $59.25
MP1: $104.45

Pre Flop: ($0.75) Hero is SB with Ah Kc
UTG calls $0.50, 4 folds, CO calls $0.50, BTN calls $0.50, Hero raises to $4, BB raises to $12, 3 folds, Hero requests TIME, 1 fold
Am I too nitty here by folding AK?  I have to believe that in 137 hands, he's had ample opportunity to 3bet...  he chooses now, in the BB, with 4 players to act, to 3bet?  I have to assume that he has AA or KK...  What would you do?

Final Pot: $9.50
BB wins $9.50