"on a slope that was steep enough and long enough you could kick up a veritable rock slide coming up behind you. Has that happened to anyone? Is it a plausible concern?"
I was on a slope in the Sierra 3 years ago that came real close to being slide prone. I was going uphill and sliding downward 8-10 feet occasionally. I wasn't concerned about getting buried, but I was concerned about getting deposited on a very slick snow band below with a nasty run out. I managed to traverse out of it, very carefully, and eventually found some scree that was more consolidated, but under a cliff that had a lot of rockfall at its base. That was why I was out above the snow band in the first place. It was one of my weirder moments in quite a while. So, yes, I'd say it is a potential concern. I think it depends on the depth of the loose stuff, the mix of particle sizes, and what type of rock you are dealing with. Shale, for instance, is very slick stuff, whereas granite is not, although the stuff I was on was pea sized granite but very deep. I'm probably missing some variables here, but those are some that come to mind.
"Also, do people have any advice on scree running technique in general?"
Uphill? Fugiddaboudit!
Downhill? When I was still doing it, I pretended I was downhill skiing. Select a line and carve turns to maintain control. It can be a real trip, especially when you start pushing the envelope. The finer scree is THE BEST. For those among you who frequent the Southern Sierra, (Dave T. are you listening?) the slope on the north side of Upper Crabtree Lake that leads up to the main Mt Whitney Trail is awesome, my personal favorite.