A Loose Shove (Filthy Bead)

My call might be a bit loose here but 
why, oh why, 
would someone want to shove 43o with a 50BB stack???

Full Tilt Poker $22 + $2 No Limit Hold'em Tournament - t15/t30 Blinds - 9 players - View hand 247063
The Official DeucesCracked.com Hand History Converter
BTN: t1485 M = 33
SB: t1470 M = 32.67
BB: t1500 M = 33.33
UTG: t1545 M = 34.33
UTG+1: t1500 M = 33.33
Hero (UTG+2): t1500 M = 33.33
MP1: t1500 M = 33.33
MP2: t1500 M = 33.33
CO: t1500 M = 33.33

Pre Flop: (t45) Hero is UTG+2 with A K
2 folds, Hero raises to t125, 1 fold, MP2 calls t125, 1 fold, BTN calls t125, 1 fold, BB raises to t1500 all in, Hero calls t1375 all in, 2 folds
Flop: (t3265) 7 7 4

Turn: (t3265) J

River: (t3265) 4

Final Pot: t3265
BB shows 4 3 (a full house, Fours full of Sevens)
Hero shows A K (two pair, Sevens and Fours)
BB wins t3265