It's certainly interesting, but I just think it can't be one of the liars, I know Toby is in the A team, but I not wnt him to be

Hmmm yeah really interesting...
Actually I kind of think you're on to something :D
I really don't want Toby to be in the A Team either, but he might be undercover or something (I hope)!!!
And at first I didn't think it would be one of the Liars, but that would actually be really good cover, plus the girls broke up for about a year so one could hold a grudge... And, I don't know if anyone else has noticed, but every time the words "liar" or "secret" or something are mentioned the camera always pans to Aria to watch her for a few seconds... Just some thoughts :D

There's also Mona's "Miss Aria, You're A Killer, Not Ezra's Wife" and the fact that nothing bad caused by A ever happens to Ezria. However, I've always had the feeling that Aria is the writers' favorite and I doubt they'd make her part of the A Team. I don't think Ezra is part of it either because of the same reason: Aria is their favorite, all her mishaps are short-lived.

It would be really interesting if Aria were on the A Team because she's, clearly, the writers' favourite and if she's on the A Team there's a high probability of Ezra's in too. It would be a good explanation for their relationship hadn't suffered to much when we compare with Hanna & Caleb or Maya & Emily...

This is a really interesting article about Aria...

link

Thanks for the link! I really like those theories. I agree, she seems the most suspicious, but I doubt she's the big A unless they plan to reveal it in the very last episode of the show.