Market does not accept meaningfull work that actually does some worthy results, that was exactly the goal of utilising BOINC (Berkeley Open Infrastructure for Network Computing is an open source middleware system for volunteer and grid computing) in GRC Gridcoin. Daily trade volume like thirty bucks, rejected.
I'm interested in this, but I don't see how BOINC has the properties needed to secure a cryptocurrency. I think a lot of people saw possible problems with it and stayed away. How did Gridcoin manage the problems involved?
First, a lot of BOINC problems are linear (fastest computer wins ALL the time, rather than in proportion to speed).
Second, it doesn't usually happen, as I understand it, that everybody is working on the SAME problem - some get easier and some get harder.
Third, it makes their servers a bottleneck and a vulnerability - people have to contact these servers to get a new problem every round, the block chain dies if the servers ever go down, and somebody could arrange to get "easy" problems if the operators collude or can be bribed.
I'm not saying there's no way for it to work; I just don't know how to engineer around these issues.