From some link somewhere:
The usual complaint is that it's too complicated for the casual viewer and Moff replies that there are pre-teens who are fully clued-up!
Moffat says:
"I think people have come to think a plot hole is something which isn't explained on screen. A plot hole is actually something that can't be explained.
Sometimes you expect the audience to put two and two together for themselves. For Sherlock, and indeed Doctor Who, I've always made the assumption that the audience is clever."
Well that clears them all up for me
Although I haven't seen Sherlock past season 1 yet