Pre-rolls — the short 10-15 second commercials that some video sites often make you watch before you get to the actual content you want to watch — are a bad idea. Here’s why: When you’re flipping the channels on the TV and you come to a channel with a commercial, do you stop and wait for it to play out, just so you can see what’s coming next? No, if you’re like the vast majority of people I’ve ever watched TV with, you keep flipping.

Now imagine you’ve just clicked on a video link. The first thing you see is an ad. NEXT.

I don’t have statistics on this but I’d bet video sites with prerolls lose an enormous number of viewers in those first 10 or 15 seconds — even if you’re clever enough, like Cnet TV, to include a countdown timer so people at least know how long they have to remain in purgatory. (Disclosure: The magazine I work for, PC Magazine, uses prerolls in its online videos.)

Much more clever is a short advertisement at the end of the video (aka a “post-roll”). You can even make this, as Revver does, a highly unobtrusive still image or a simple flash animation. That way you get people in a happy state, after they’ve just watched your funny 2-minute video, and at the very least you’re not pissing them off or making them wait.

Nevertheless, I predict that pre-rolls will not go away. In fact, they’ll abound on video sites for years to come, and you’ll probably see even more of them in 2007, for the same reason that popups and pop-unders still haven’t gone away: They sell.