FORTUNE — It’s been nearly a week since word first leaked that Microsoft MSFT has agreed to acquire Yammer, the San Franicsco-based enterprise social networking company that many had viewed as a 2013 IPO candidate. So where’s the announcement?

This isn’t the sort of thing that Microsoft could, or would want to, keep under wraps. The deal reportedly is worth around $1.2 billion, and helps Microsoft fill a large enterprise collaboration hole that SharePoint alone couldn’t handle.

A source familiar with the situation tells me that the deal has been signed, but that Microsoft delayed the formal announcement so that it wouldn’t clash with yesterday’s Surface launch. Not sure if Microsoft was worried that Yammer would overshadow Surface, or vice versa.

Either way, expect the Yammer deal to be announced shortly. The only hold-up is on the PR side, not the business side.

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