I've had this same issue with my 2011 MacBook Air 11"
Often I'll be using the trackpad as usual, with Tap-To-Click not enabled in the settigns, and my trackpad register clicks even if I don't depress the button but simply have my finger on it. I'll also be scrolling, and I'll get text begin to highlight as if I'm clicking and dragging, but I'm not. Sometimes I can't even scroll with two fingers, and images and things will begin dragging to places on the desktop as if I have the button pressed down all the way, but I don't.
I set up a Genius appiontment about three weeks ago and went, but the Apple Genius couldn't replicate the issue, and it did happen twice while i was uing it, but he blamed me for the issue and said that I was probably clicking the button but couldn't tell if I was or not. I've noticed that it often happens when I'm using it on my bed, and I think it has to do with the case not being absolutely flat and the MacBook Air being too thin to function properly, so when I get the issue, I always have to sort of move the Air around, and put some pressure all around the machine to try to get it to "set" or something.
But this issue also occurs almost daily when I use the machine in class on a desk on a flat surface. So I don't know why my $1,500 machine isn't functioning properly. And I'm very upset that Apple won't do a thing about fixing it, even if it's still under warranty! That's what a warranty is for, and they're just looking the other way. I've also called the Apple support line since I was within the 90 days, and they couldn't help me either.