OpenID integration doesn't create an easy way for end users to share their likes with hundreds of Facebook friends who read newsfeeds on a daily basis, or tell you that 30 of your friends have become members. Love it or loathe it, there's a big value-add for marketers (and depending on the application, possibly also end-users) to Facebook Connect over a simple universal authentication system.
As others have pointed out, OpenID isn't even better than Facebook at what it specialises in: at best OpenID asks the user to remember whether they signed up with their Yahoo ID or their Gmail one and at worst to read a third-party FAQ just to figure out how to log in. Facebook Connect is a big blue button with a recognisable brand, and you're quite possibly already logged in.
As others have pointed out, OpenID isn't even better than Facebook at what it specialises in: at best OpenID asks the user to remember whether they signed up with their Yahoo ID or their Gmail one and at worst to read a third-party FAQ just to figure out how to log in. Facebook Connect is a big blue button with a recognisable brand, and you're quite possibly already logged in.
If only their API wasn't such a piece of shit...