One thing to consider is that, one doesn't just GPU mine YaCoins. GPU mining YACs has to be more profitable than CPU mining YACs + GPU mining something else, otherwise it's a waste. Anyone doing it would have to believe YAC value would skyrocket.
At it's current prices, YAC isn't profitable to mine, with anything
Lol. at .00001 YAC is profitable to mine for a lot of people. Remove electric and server costs (and thief's and botnets) and there is likely a population with access to cputime with $0 cost. I know a lot of call centers with hundreds of low power seldom used PC's. If each gets 10Khash and the electric is included in rent, a system admin could easily work out a profit sharing deal to use the PC's on off hours. Even at $1 a month once automated it's profitable.