No, World Community Grid guarantees their researchers that they will use at least a quorum of three. As I'm sure you will appreciate, humanitarian problems are less error tolerant than searching for aliens. With a quorum of two, it would be possible (but not probable) for two work units to fail in the same way. Quorum of three gives a very small statistical error, and makes the results a lot more reliable.

World Community Grid are constantly analysing grid performance, and if the error rate for a particular project was low enough, then I'm sure WCG would recommend switching to quorum of two. However, it doesn't seem suitable for any of the current projects.