The whole point of Bitcoin is decentralization, removing the requirement for trust, etc. The idea of a centralized foundation vested with representing, effectively, the entirety of "Bitcoin's Interests" strikes me as diametrically opposed to that concept. The members of the foundation have various interests that may or may not be in keeping with the spirit of Bitcoin, and such an organization provides perfect cover for re-making Bitcoin in their image.
This first occurred to me when the foundation became the de facto spokesbody in response to Congressional and regulatory inquiry. How did these self-appointed people suddenly have the right to decide what regulation, etc. was acceptable to the whole of the Bitcoin community?
Surely, there needs to be some advocacy. But, it seems that such advocacy would take a more radical, de-centralized, democratic form that is more akin to Bitcoin itself.