For mobile game developers, Apple’s Game Center may be one of the most important developments this year. The social networking platform is coming to users with iOS 4.1, and available to developers now as part of 4.1′s third beta, which AppleInsider recently looked at.

Now that more of Game Center’s features are coming to light, it’s becoming evident that Apple is building something closer to an existing game network like Xbox Live than a standard social network.

The initial sign-in to Game Center uses the Apple ID, but users will be identified to each other by a nickname. Apple likely expects players to connect with people they don’t know for real-time multiplayer, unlike Facebook’s asynchronous games, which are played mainly by real-life friends.

However, there’s also a prominent “Find Me By Email” option, which suggests that Apple is also hoping to connect people who do know each other — thus taking advantage of both game networking styles. At the moment, there’s no obvious tie-in to Facebook accounts.

Since every iDevice user will potentially be part of Game Center, it should prove valuable to existing social platforms like OpenFeint and Plus+, which have had to ask players to sign up thus far.

Those services seem to be counting on Apple giving access through an API. Since Game Center was announced in April, the independent platforms have been working on new features beyond leaderboards and challenges — which should be part of Game Center — to differentiate themselves.