Kevin Systrom, cofounder of Instagram. (Twitter)

If this is true, it sure does shed some light on the abrupt end of Jack Dorsey’s Instagramming. VentureBeat claims that rumored offer from Twitter was solid enough to give CEO Kevin Systrom quite a bit of leverage, which he did not let go to waste. Their sources claim Mr. Systrom used the company's pending Series B to get a "very real offer in the hundreds of millions of dollars range" from Twitter, and that's when it gets really interesting:

Twitter chairman Jack Dorsey, an early Instagram investor and a one-time avid photo-sharer, was said to be involved in all aspects of the deal. But Instagram shrewdly did not sign the term sheet, which would have bound it to a no-shop clause, and went ahead and closed its financing round.

This put Systrom in an odd — but useful — situation in which he had both the new funding and the Twitter offer still on the table. According to one source, Systrom went to Zuckerberg for a better deal and Zuckerberg bid just to block the Twitter deal.

But this should be taken with a grain of salt. Previous reports have Mark Zuckerberg making the initial outreach, in the form of an April 5th phone call. It's also likely that, as the Wall Street Journal reports, it wasn't just the prospect of a Twitter offer but also the runaway success of Instagram's Android app that worried Mr. Zuckerberg.

Anyway, if we learned anything from The Social Network, it's that you don't get to $1 billion dollars without making a few enemies.