Updated policies spell out that using Facebook for any product or service that replicates one of its core features isn't going to be tolerated unless Facebook gets something in return.

Facebook recently introduced its new internal search engine, Social Graph, at an event that had been hyped up by being shrouded in mystery. It invited devs to sign up for a "very limited beta".

Then within a matter of days Facebook abruptly blocked services including Vine, Twitter's new video-sharing app, and Wonder, a social search app from Yandex, the Russian-based search engine

The clamp down seems at odds with the way in which Facebook has encouraged app developers on the Web and on mobile devices to use Facebook as a default login and a way of app users finding friends for the purpose of sharing apps and gaining new users.

However, Facebook rules have always made it clear that it would not tolerate exporting data into competing social networks.

The old rule I.10 read:

• Competing social networks:
  (a) You may not use Facebook Platform to export user data into a competing social network without our permission;
  (b) Apps on Facebook may not integrate, link to, promote, distribute, or redirect to any app on any other competing social network.

The new rule reads:

• Reciprocity and Replicating core functionality:
  (a) Reciprocity: Facebook Platform enables developers to build personalized, social experiences via the Graph API and related APIs. If you use any Facebook APIs to build personalized or social experiences, you must also enable people to easily share their experiences back with people on Facebook.
  (b) Replicating core functionality: You may not use Facebook Platform to promote, or to export user data to, a product or service that replicates a core Facebook product or service without our permission.

Alerting devs to the change on the Facebook Developer blog, Justin Osofsky writes:

For the vast majority of developers building social apps and games, keep doing what you’re doing. Our goal is to provide a platform that gives people an easy way to login to your apps, create personalized and social experiences, and easily share what they’re doing in your apps with people on Facebook. This is how our platform has been used by the most popular categories of apps, such as games, music, fitness, news and general lifestyle apps.

He then refers to "a much smaller number of apps that are using Facebook to either replicate our functionality or bootstrap their growth in a way that creates little value for people on Facebook" making it obvious that the policy clarification is indeed intended to curb their behavior.

Is this fair?

Intrinsically the rule is fair to Facebook, but how fair it is to developers depends very much on how it is implemented and interpreted. There is still a lot that is vague in the new rules and it depends on how aggressively they are going to be enforced.

We all need to remember that when you play with a monopoly, you play by the monopoly's rules - whether you like them or not.