The FEC did NOT say that PACs can't accept Bitcoin. They pretty much unanimously agreed during the meeting (audio) that PACs *can* accept Bitcoin, and the Libertarians and some candidates already were and continue to do so.
They just couldn't decide *how* PACs should accept Bitcoin, and CAF (the requester) didn't ask about accounting standards or the like, so they didn't approve the request. FEC decisions are ternary: yes, no, and nil. This is nil, not no.
Full disclosure: my PAC's comments explaining a bunch of problems with the proposal were one of the primary reasons why they didn't rule on it, and we're intending to file a new request in the very near future. (Comments welcome on our draft of a new safe harbor policy.)