Oooh. Good point. Thanks!

In fact, I guess a half circle cut out of the striker, then sharpened like a serrated edge would be best.

Edit:

Ya know... given that the preferred technique seems to be "hold the striker, move the steel", what do you all think of a striker designed specifically for this. I'm thinking a rectangluar piece with a hole near one end. The edges of the hole are sharpened, and the hole is, say, 2 or 3 inches from one end (to position the sparks over the tinder). There'd be just enough metal above the hole to use to hold the striker. To use, simply position the striker, insert the steel, push down and pull back.