Facebook is building a network for professionals to connect and collaborate on work-related documents.
Users of the separate Messenger app have more than doubled from 200 million in April, the company said.
Users will be able to connect directly to the social network via anonymizing service Tor.
An app launched by Samaritans notifies Twitter users if people they follow seem to be distressed.
Timeline views per user, a key measure of user engagement, dropped 7% in Q3.
The site said it had won more than $2B from scam artists who sold fake likes to businesses.
Investment in mobile messaging service may value the start-up at about $10B, reports say.
Ad-free social media platform Ello overcomes a technical setback to continue its rapid growth.
Tens of millions have made China Apple's third-largest market for software sales.
Dmitry Medvedev's Twitter feed featured posts stating he had resigned and was ashamed of the government.
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