As members of our editorial team noticed today, the Instagram app now notifies you when Facebook  and Twitter  friends join the service. Foursquare already does the same thing. But this integration could swiftly kick up activity, and by extension user numbers, on the photo sharing service with its estimated 50 million  subscriberes. Signs of a Facebook-Instagram alliance started in early January, well before Facebook bought the app-maker, when Instagram started displaying full-size photos  on Facebook profiles when both accounts were linked. By comparison, plush and expanded interactive cross-posts was an addition Twitter only just added  to its Facebook display.
The Facebook-Instagram relationship is increasingly well watched. It has the attention of the Federal Trade Commission, which wants a closer look  at the deal as a routine check performed on acquisitions of over $68.2 million. It was also under scrutiny from the SEC  in Facebook's pre-IPO days, and in the weeks since, questions have been raised about Instagram's real value as Facebook's share price slides. Facebook's relationship with Instagram may have been complicated by the puzzling launch of its own Facebook Camera app  after the acquisition announcement, but it seems the two are committed to being friends.
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