I've watched that play to Crabtree more and more today... and interference could definitely been called. The reason I don't get too wound up about it is because it looked like Crabtree was pushing off a bit on Smith's helmet. Plus, the refs seemed to really let the defensive players have as much play as the receivers all game long. Then again, I can understand here it's for the championship title.
To me the worse non-call was why the refs never called a single penalty for holding on that punt-safety. Jim H had no problem with the play itself, saying "you're coached to do that", and it makes sense. But a penalty while still getting a safety, stops the clock sooner, enough time that the Niners might - and I emphasize "might" - have given them time for a run back and one kick to tie it up.
Truth be told, I was surprised the Niners kept passing there on that stand. The running game had been going strong especially up the middle. I can see one, maybe two passing plays but four?
Eh.... it's all over and the Ravens earned it. Wasn't the cleanest game, but it wasn't the worst, either.