This is a cool deal, but I have a quibble: The cost to you of donating $50 is not $0, but...$50. Relative to your not-having-donated self, your having-donated self is $50 poorer.
Granted, this might be more than compensated for by the warm fuzzies and so on. But if $50 is too much for you to donate out of pocket, then it's also probably too much for you to donate when the money is a gift.
OK, well, feel free to take the free $50 and not give it to SIAI. I won't tell anyone.
If I gave you $50 you hadn't planned on receiving, would you consider giving it to charity?
Here's your chance to find out.
Just in time for the Tallin-Evans matching fundraiser, ING Direct has started offering a free $50 cash sign-up bonus. I've personally used ING for 10 years and referred over 20 people to similar promotions of theirs in the past so I can confirm that this is legit.1
It's a simple, effective way to get started as an optimal philanthropist for free:
Full disclosure: I was an SIAI Visiting Fellow in 2010. I've also used ING Direct as a customer the past 10 years, but otherwise have no financial interest in them.
[1] This isn't one of those bogus "intro" deals where you have to make sure you cancel the service later on or risk getting charged fees. ING has no fees, no minimum balance requirements, no sleazy marketing emails, and consistently good savings rates. If you want to use them for their good service after signing up, great, if not, no worries. All you have to do to qualify for the $50 is make 3 small purchases you were planning to make anyway with their new debit card. I know it's a trivial inconvenience, but I think it's worth it to be able to donate up to $100 to charity without actually spending any money.
[2] Profit denominated in warm fuzzies, karma, and post-Singularity catgirls.