There's a lot to say about Robin Hanson's argument, and I don't think it's as clear-cut as he makes it out to be, e.g. there are critical comments in this thread:
I wish he wouldn't try to figure out what hidden motive prevents people from following his strategy before it's even been established as the best strategy.
http://lesswrong.com/lw/h3q/a_rational_altruist_punch_in_the...
I wish he wouldn't try to figure out what hidden motive prevents people from following his strategy before it's even been established as the best strategy.