I'm not sure that the Beatles can be equated to Justin Bieber, exactly. I think the screaming girls around the Beatles were mostly older than the pre-teens surrounding Justin Bieber.
I'm not denying the existence of the 'screaming girl demographic'. I myself was the proud owner of The Partridge Family Album, back in the day. But this was at age 9 or 10...before I discovered Led Zeppelin and Grand Funk Railroad.

I do not remember Beatlemania - by the time they came on my radar in the 70's, that part was long over. But on the tapes I see of Beatlemania, most of the girls look to be in their late teens/early 20's. Not in the 11 to 15 age group like Justin Bieber.
I know that to guys, the 'screaming girl demographic' is all one big pie. But to those of us who lived it, I think it's sort of in two stages.
First comes the Justin Bieber/David Cassidy/Shawn Cassidy/Donny Osmond/Leif Whats-his-name stage....for many of us girls, one of these guys or someone like him was our first crush as a pre-teen.
Then when you are a little older, if you have not moved on to rock, but are still only listening to pop, you get into the Beatles/Backstreet Boys/NSYNC/Hansen/Jonas Brothers stage.
Perhaps a small technicality to you guys...but to those of us who lived it as young girls, significant. At that point, we have at least started the transition to something resembling listenable music and have begun to outgrow the idea that the most important quality in a pop star is that he be 'cute'.
