TMQ says that he thinks the call was an either-way call on that 4th down. (And I did not realize that AJ Jenkins was in the game--why?) But he points this out:
The endgame down that troubled TMQ was third-and-goal from the 5. Crabtree went in motion right, then ran a shallow out right -- a West Coast play that was a favorite of Bill Walsh's in this situation. Crabtree sure looked like he caught the ball, putting both feet down, then heading upfield. He was drilled helmet-to-helmet by nickelback Jimmy Smith. The ball came out and went out of bounds at the Baltimore 4. Zebras ruled incompletion.

If the pass was never caught, then Crabtree was a "defenseless receiver" and the helmet-to-helmet hit should have been a personal foul. If the pass had been caught and Crabtree was "re-established," contact with his helmet was legal. But then the ruling should have been completed pass with a fumble out of bounds, advancing the spot to the Ravens 4.