Watch the theme song very closely, "Ali's" hair apears to be brown, and colored blonde. Maybe it wasn't Ali? And my A suspects :
-it is too obvious to be CeCe
-Jenna and Shana don't know what really is going on, so no for them
-if it is so shocking, it has to be someone close to the liars, maybe family or a boyfriend/girlfriend
-I don't think it was Mrs. Mongomerey because she is in Austria, and still the girls get messages from A
-or Mike because he just wants to protect Aria
-Bryon is suspicious
-so is Jason and Caleb, especially since Caleb is a very good hacker
-not Melissa, because she explains to Spencer that she has been protecting her
-maybe Toby
-but my biggest bet is that it is aria, because do you see the way she writes her A's are like the A, and the day after Mona's laptop's info dissapears and kisses appear on the screen, and the liars get messages ending in "Kisses A", Aria's shirt is covered in kisses
-her motive might be that Ali and the girls ruined her family, and I think she has an acomplice, because her handwriting is neater that A's, and with this acomplice they could support each other with good alibi's
Well tell me what y'all think!