If Crabtree is the first read in a progression (which he is most of the time), then Smith is probably going through the progressions and thats when the line breaks down, so yeah he probably is forcing it there a little bit. I dont think we would see this as a problem if the line could hold up for more than 2 seconds.
More often than not, there are 4 guys on the line that are blocking and the 5th guy lets his guy blow right by him. Its not necessarily the same guy getting beat either. I cant remember the last time when one of our QBs dropped back and you heard the broadcasters say, "________ drops back to pass.......he has a lot of time......throws to _______ for a ___ yard completion. If the ______ are going to beat the 49ers they are going to have to get better pressure on the Quarterback."