It seems a bit odd to use your computer resources to mine bitcoins and then donate them to SETI or folding@home when you could simply donate some computer power to those projects directly.
There are over 50 BOINC projects and some are better or more "worthwhile" than others. SETI might be well known, but many in the BOINC community dislike it for various reasons.
However, running computer time for things like SETI (normally CPU) doesn't pay their bills and feed the interns who often do the day-to-day work. Donating some of the GPU generated coins helps.