Wrong question. The right question is: Who facebook already sold their equivalent system to? or else, what facebook is using it for?

Zuckerberg has an agenda: http://gizmodo.com/former-facebook-workers-we-routinely-supp...

Facebook ToS [0];

> You will not collect users' content or information, or otherwise access Facebook, using automated means (such as harvesting bots, robots, spiders, or scrapers) without our prior permission.

Rate Limiting on the Graph API [1];

> Your app can make 200 calls per hour per user in aggregate.

The Graph API terms, and end-user terms are lengthy, I'm sure someone else could better answer this, but I don't believe a developer would get away with it via the API, due to the rate limit, and a raw-HTTP image scraper would not be possible due to the randomly named images Facebook assigns.

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[0] https://www.facebook.com/legal/terms

[1] https://developers.facebook.com/docs/graph-api/advanced/rate...

Facebook doesn't allow this, but even if they did, there are many laws in place in western countries regarding photographs of people in public, that would make creating and/or using such an app illegal.