Not very many people have a state-of-the-art supercomputer in their basement, so it wouldn't be that useful.

IBM's using two racks of computers and a huge SAN. Maybe it couldn't compete with watson, but a decent setup could be cobbled together for 5,000. It wouldn't be as fast, or as comprehensive, but it could be done.

The harder part is the tens of thousands of man hours with very smart people.

I think a little project called Linux got tens of thousands of man hours with very smart people ... Just saying.

True, but you can rent something like a state-of-the-art supercomputer from Amazon for fairly reasonable hourly rate. Watson has 90 8-core servers and 16Tb of RAM - to rent 100 Quadruple Extra Large instances (1600 cores, but "only" ~2.3Tb of RAM) would cost you $160/hour. I'm sure there are many other differences (and the fact that you can't fire up that many cluster instances without calling Amazon first), but the idea that an open source package like Watson wouldn't be useful doesn't make sense to me.

And IBM did state that they could run the Watson software on 1 system. (It just took 7 hours to get the confidence level - not 3 seconds)

I think this is a bit short-sighted. Attempting the problem within constraints imposed by not having deep pockets could be very useful.