Yeah, unless the users choose charities that alienate other users. Is your pageview going the planned parenthood or the NRA? Berkshire Hathaway discontinued their shareholder directed charity because some (vocal) people disapproved of the choices: http://www.berkshirehathaway.com/news/jul0303.pdf
Anyway I wish them the best but I hope they know what they're getting into.
They do seem to be thinking about exactly the sorts of problems you are talking about. Not quite clear in the techcrunch blurb, but more explicitly stated in the actual reddit blog post:
I hadn't thought of that before. If charities like Planned Parenthood (apropos the Berkshire Hathaway situation) or the WinShape Foundation (remember the Chick-fil-A incident?) are on the table, there could be controversy.
Anyway I wish them the best but I hope they know what they're getting into.