Pretty Little Liars: Connections and Questions

In my book Pretty Little Liars, there are many connections in the real world to make to this book.  One example would be the fact of all the mean, and anonymous users.  There are sites in real life where kids go on anonymous accounts and cyber bully other innocent kids just like them.  Usually, they don't even have a reason, maybe just jealousy... which brings me to a question about my book.  I wonder why this "A" is attacking these girls? Is he/she jealous or did the girls do something to them in the past?  It's exactly like what happens in real life if you think of it.  Ya, you may say someone acting like a dead girl to attack innocent... or not innocent girls.... is crazy, but really, this same thing is happening in our society today in different forms and that's a huge problem.  Another question I have is how this anonymous user knows so much about the 4 girls?  And how long have they been watching them?  It's actually a pretty creepy concept to think about.  I predict in the next book of the series, I may find out some more about A's intensions but I won't find out who a is.