What's with the levitating cans?

There was a recent controversy about the iceman beer pour amongst some of my fellow beer nerds. Filling glasses to the brim is for some people offensive to the eye it seems. Personally it's not something that's ever bothered me, I just assumed people were doing it so they didn't get the problem of the head collapsing when they're trying to take a photo. No, the thing that disturbs me is the levitating beer cans.

What sorcery is this?

Before taking a photo of a canned beer the in thing now is to attach the empty can to the glass, as in the picture above. This freaked me out a bit when I first saw it. "What sorcery is this?" I thought. But let's face it magicians are basically liars, and nothing supernatural is involved. Nowadays cans will attach quite easily to glasses, but it still makes me do a double take when I see a can apparently floating next to a beer glass.