I'm just finishing up on a SharePoint 2010 external facing implementation.
Normally the recommended configuration for that kind of environment is to
point it at a separate AD or Active Directory Services implementation in the
DMZ that has a one way trust to the internal AD. Accounts inside the
firewall can then be given access to the SharePoint implementation in the
DMZ, but accounts in DMZ AD can't be given access to internal resources.
Take a look at the extranet topologies diagram from MS. I used something
similar to the Back to Back perimeter topology.

Maybe I am misunderstanding...I was assuming that this would not be an extranet
environment. We would be building a community site that is externally facing
and would allow anonymous access to everyone to view content but you would have
to log in to add content (ie. blogs, discussions). If a user wanted to add
content, they would create a profile and log into the site to add their content.
I would want the site to manage the account creation. In that scenario, would
you still set it up like an extranet against AD?

Your Service Accounts, Farm Admins, etc would still be AD accounts, so you
will need an AD. In the system I just finished implementing site updates
(like new content types, lists, sites, etc.) are handled by users using
their internal AD accounts. Other content is handled via FBA users.

Hi, I am new to this forum but we are trying to implement something identical i.e. community sites that are accesible by external users e.g. non-employees such as customers and suppliers. Robby Barr you mentioned that you just finished implementing something similar. Can i ask if you segrated the external communities by web application so that the external users had communities with a different url? Also, how long did it take you to do and was there bespoke development required? Thanks.