These results are really cool because first when you look at such a problem space, the size may look insurmountable but with clever algorithms one can always hope to solve it in reasonable time. Whether 35 CPU years is reasonable, I don't know. :)
I wonder why Google donated spare cycles to solve the Rubik's cube when there are problems like Fold.it that could use it for science.
Folding and SETI have been at it for decades, and will be for decades more. That'd be a lot of power/hardware costs for little net gain modulo time spent.
(Note: 30 cpu years really isn't a lot of time when you start getting truly massive parallelism, and google is certainly at that scale. I'm honestly surprised to see this is pthreads based, I would have expected it to lean heavily on CUDA (or maybe I'm just showing my naivete to the field of parallel programming))
35 CPU years = 35 * 365 = 12,775 CPU days
Let's assume that your standard Google machine has 2 8-core processors, that is 16 cores per machine
12,775 / 16 = 798 machines
800 machines is a lot for your average person, but for a company like Google it is a very small drop in the bucket. And that is assuming you need to do all of the calculations in one day. If you are willing to do the calculations over a month, you only need 26 machines.
Even if "CPU year" applies to one 8-core processor, that still means it is just 26 * 8 = 416 machines, which is a very small number for Google.
And remember, the machines are still doing other things, this is just using idle CPU (generally a plentiful resource for your standard internet giant workload).
An equally absurd question: Why doesn't google use all of it's man/computing power for science instead of trying to make money from internet ads?
One day someone will turn lead into gold. There will never be a "good" reason to do that, but the history behind it is sufficient. There's nothing wrong with taking some pride in accomplishing something you've always wanted to do.
The idea that someone somewhere should pick a goal and then all the resources anyone could conceivably spare must be devoted to it, on pain of a designation of "immoral", is a little more disturbing to me.