The benefit of 529 college savings plans for U.S. residents is that interest and dividends are not taxed each year and that capital gains are not taxed when funds are used for college. To pay for free community college, the President is proposing to fully tax the gains of 529 plans
http://reason.com/blog/2015/01/19/lets-pay-for-free-community-college-by-t .
I think I will still contribute to 529 plans, since I doubt their tax benefits will be revoked (Congress will likely not go along), but there is now some political risk to those benefits.
