There are already several crypto currencies that are distributed dependent WCG points.
I don't see a benefit of another one. Besides that, this creates several problems, for example cheating will become a much larger problem than it is now. I would not recommend WCG to become directly involved in that kind of thing.

Besides that: someone has to pay for the hardware and electricity that runs World Community Grid, crypto or not. If the volunteers are paid with crypto and cover their costs with that, someone else has to pay (namely the poor guys who buy the crypto from them and lose everything in the end, when its value ultimately goes to zero). I don't think that makes the world any better after all, besides drawing some short-term attention and increased WCG output for some time.

WCG (more IBM really) would have to worry about larger things like did the Coin count as a Security? Cryptos are still the Wild West with few laws that actually outline anything to go by.