familiarity
aesthetics
trust
ease of use
Inconsistent, but improving (see Google LSO and JanRain RPX)
could be applicable to more people as it does offer more sources of identity, user choice / transferable
already richly populated for many people
limited to what FB chooses to expose
single persona
tends towards private
arguably secure
password only protection (no strong auth)
limited only by developer imagination
slowly becoming more viable (via Google Social Graph API, OAuth, Portable Contacts, example)
security conscious but so new it's unclear how phishable eg.
option for stronger authentication
decisive
brand power
marketing power
consensus
broader pool of innovators
Unified conversations on social web (i.e. not Facebook only, Google only, etc.)
huge and self aware
larger, potentially, though currently unaware and disinterested
off-site activities published to the huge Facebook ecosystem via Newsfeed
possibilities limited only by imagination, politics
Easy for Facebook
Requires ongoing support for multiple proprietary vendors if desired
Easy, consistent support for all open standard ID and data providers
Centralised
One persona: your civil identity since Facebook requires real name
Compartmentalisation under that one identity is possible, but Facebook keeps oversight over all of the different contexts you use your account for
Decentralised
Multiple OpenID accounts for multiple, non-linkable personas
OpenID: only authentication, no trust. Trust depends on online reputation of url that is claimed.
