To defend the show for a moment though, wasn't it Mona who was the original A from the Halloween flashback, sending the notes on it being my turn to torture you? As far as I'm aware A was just supposed to be Mona for the first two seasons, hence the irony in Mona convincing Allison to run away for protection when she was A all along.

Hmmm, I'm not entirely sure. It's highly probable and it makes sense, though the confirmation about that has been rather vague.

Although, it begs to question who had been stalking Alison during her time in hiding? Was it Cece basically wanting her to come out of hiding? Unless that is the Uber "A" that has been said will happen at some point. There's just a lot of unanswered questions about the series of events throughout the timeline who "A" tormenting them all, from Alison to the rest of the girls. Some of it was Mona, then it was Cece, but then there were other instances that I'm just scratching my head about.