Hope have a weaker over cam action than a lot of others. If you get the Ti version, which has a more elastic property than the steel version, then you've an increased chance of them coming loose/undone.
I've always thought that they were a bit dodgy having tried some about 6 years ago. Never trusted them and went back to good ole' Shimano XT which you can clamp down like crazy. "they are no different from any other cam over skewers."
Maybe they've redisigned them, cos my set have a bloody good and positive cam over action. Better by far than the Mavic QR's I have on my HT which have come loose (suspect by cycling in long grass)