fbdev021308.pngFacebook is in a running battle to develop its platform live — while developers are building applications and users are using those applications. Its latest big change: Implementing a flexible system for inviting your friends to applications, designed to promote the apps that people like the most, but which punishes abusers of the invite process.

Facebook has the largest, most advanced developer platform to date. By fine-tuning it with changes like this, it hopes to maintain a better experience for users, and keep developers (and users) from spending time on rival MySpace. These platforms, as I’ve covered, are making developers an increasing amount of money.

Requests per application will now be based on the “affinity” that a user shows for an app, according to Facebook’s Tom Whitnah. While the company isn’t providing all the details, this affinity will include the rate that a user accepts and ignore requests from others for an app, as well as whether or not an application ignores user requests to skip inviting their friends.

fbdev2021308.pngInvite requests were formerly invited to 20 per person per application per day (pictured), but now that number is out the window.

This mirrors a similar change that Facebook made to notifications that appear within a user’s homepage, about things like actions their friends take within applications.

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Earlier today, Facebook warned some developers that their apps were forcing users to invite friends before they could use the app themselves, Inside Facebook’s Justin Smith reports. Those apps will be disabled until they correct their behavior.

Facebook has frequently changed the “rules” of its developer platform since it launched last May. The company’s strategy is to launch first, then refine the rules as it sees what works and what doesn’t. Live testing is often the best way to figure out the crucial nuances of software design. However, I’ve been hearing rumblings from developers about some changes, such as the lessened prominence in users news feeds about actions taken by their friends in apps.

Rival MySpace is trying to take advantage of Facebook app developer dissatisfaction. It is trying to present its new developer platform — not yet available to users — as a better-explained alternative. The company has promised to do a better job than Facebook, it has said, of setting clear rules from the start, giving lots of advance notice, and not immediately and automatically disabling applications that get defined as violators by a platform rule changes.

Regardless of how well that strategy works, Facebook app developers have been relatively quiet since the notifications change was put into place. Nobody’s been getting punished too bad, and the better apps do indeed seem to be winning.