Even if you get 100 Less Wrongers to register, it seems that the expected number of transplant patient lives saved will be less than the expected number of malaria victims saved by giving $40 yourself to AMF. It seems that wasting people's time (which works in small increments through willpower depletion, interrupting serendipity and other probabilistic or finely graduated effects), or conversely producing an interesting post and discussion about efficient charity (I enjoyed the post), will altruistically dominate the marrow effects.

ETA: Also, if you're going to pitch thousands of people, it's much, much, better for you to do that kind of basic background work rather than make the readers either go on faith or wastefully spend more cycles in parallel. General rule: if you can save the average reader 1 minute of processing with 20 minutes of work, that's a good deal.