If too many users report spam from an app, Facebook will restrict its distribution.

WSJ: Tensions Rise Between Facebook, Developers

Users can report spam and flag deceitful posts, but that is the extent of it.

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At Facebook, the company's site-integrity team spends its days and nights scanning for spikes in what users report as spam, and other unusual activity, such as friend request rejections.

WSJ: Spam Finds a New Target

The FTC said studies from other countries, including Canada and Finland, "similarly report a decrease in the amount of spam reaching consumers' inboxes".

BBC: NEWS | Technology | US 'winning war' on e-mail spam

This month, the report honed in on a species of brand hijacking that clogs in-boxes daily: spam e-mails hawking name-brand discount drugs.

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