Heh I got a "free" touchdown because of this in a game last night - they brought 7, I was in shotgun, left my TE wide open - easy TD.
I get a lot of completions to the TE that way because the blitzing like that. If they left the MLB back there, they might have a chance as I'd have to wait until the TE crosses him or beats him if man coverage. But when the whole second level is gone and I'm throwing quick routes...yeah.