The Instagram rumors just keep coming. First we heard Facebook beat Twitter to Instagram. Then we heard Facebook is going public on May 17/24, depending on the Instagram deal. Last night we heard Instagram CEO Kevin Systrom wanted $2 billion from Facebook.

Now, we're hearing more details about how much Facebook reportedly offered to pay for Instagram, and what that means the social networking giant is valued at: over $75 billion. This is up from the $50 billion valuation Facebook valued itself at in December 2010 when it announced it had raised $1.5 billion.

Here's the phrase I use every time I write yet another Instagram article: "Facebook announced plans to acquire Instagram for approximately $1 billion in cash and stock." The words "approximately" as well as "cash and stock" are key.

The latest rumor shows exactly why. Here's a quote from The New York Times:

In early April, Facebook bought the photo-sharing service for $1 billion, agreeing to pay roughly 30 percent in cash and 70 percent in stock, according to people briefed on the negotiations. At that level, Facebook is pegging its own stock price at roughly $30 a share. Based on those numbers, the giant social network is valued at north of $75 billion. But Facebook could actually be worth more. During the negotiations with Instagram, the parties framed the deal around a logical assumption: Facebook could soon trade publicly at a much higher market value. As part of the talks, the companies discussed a potential value of about $104 billion for Facebook, the people briefed on the negotiations said. Instagram's co-founder Kevin Systrom first broached the number, one of the people said.

In other words, if Facebook ends up going public at more than $75 billion, it will have paid more than $1 billion for Instagram. That's certainly possible, given that the last Facebook valuation on secondary markets was $102.8 billion, the highest yet.

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