I had to go through one last year in Dallas-Ft. Worth airport; only one occurrance of all the trips I made last year (probably a dozen). I assume that it's a random screening. As far as I know, DFW only has them in Terminal D (international).

I had a lighter weight kilt on (either SWK or USAK semi-trad, don't remember for sure), and it did get blown up almost enough to be interesting. The puffing lasts a couple of seconds. I had my arms down at my sides, but in hind sight, should have gatheres at least the side pleats and held them down to minimize the lift.