You CAN heel strike in flats. Here's positive proof. ;)

 Lol, but he is

Lol, but he is walking....walking mechanics are different from running ;-)
 
 well....in all fairness, he

well....in all fairness, he should get some sort of commendation for his incredible fashion sense!
 
You can heel strike in bare

You can heel strike in bare feet too. Barefoot Rick (who has run 60+ barefoot marathons) heel strikes. I've run with him, and I've seen it. How he hasn't developed heel spurs, I have no idea.
 
good grief that heel strike

good grief that heel strike looks painful, it's almost like he's striking with his achilles :p
 
I heel strike quite a bit

I heel strike quite a bit still too, especially in KSOs and when doing speedwork. You get used to it just like you get used to the feel of forefoot striking. Doesn't hurt, but you can feel the impact shoot up your leg sometimes.

I don't do it a lot though because it's never been my natural gait. I just do it because I can. And I'm not entirely convinced that a little bit of heel strike with a high cadence and short strides is a horrible thing.