- Interact with the legal system, where a centralized entity is needed: for example, to hold the Bitcoin trademark, own/control the bitcoin.org domain name, etc.
- Act as a central library for accurate information about Bitcoin, so journalists and policymakers have an 'official' place to learn about Bitcoin.
- Collect donations to fund infrastructure necessary for Bitcoin's growth (organize regular developers' conferences or get-togethers maybe? pay for development of cross-implementation testing tools? pay core developers' salaries? create a certification/testing program for Bitcoin implementations? create a central clearinghouse for information about legal issues surrounding Bitcoin across the world?)
Only the last item on this list seems good. Collecting (bitcoin!) donations to fund infrastructure is a good idea. The other two items don't please me. There should be no "official face" for bitcoin. If you want to create a support group like Bitcoin Consultancy for example, and make this group non-profit, that's fine. But don't call it "Official Bitcoin Foundation". People should understand that bitcoin has no "owner", no official face.
It would be particularly important that this group is not referenced by the main project's page, bitcoin.org. The same way bitcoin.org link to these forums was cut, no link from bitcoin.org to any bitcoin foundation should be made, at least not as if it was the only one. It should be made explicit that multiple foundations can/should exist.