2 billion searches. Per day. This bombshell inexplicably slipped under the radar in most digital marketing circles, and I do believe we've got genuine disruption on the horizon from the Big Blue.

Whilst Facebook only indexes its own internal content in the form of its 2.5 trillion posts at the moment, the inevitable question we must ask is when it will branch out into indexing external content?

We're already well conditioned to using Facebook's Open Graph Protocol (OGP) when building sites and marking up pages: Facebook therefore already has access to a solid (if concise) summary of a given page's content.

Is Facebook likely to leverage its search capability on external sites and draw those in to its internal results, stacking external content with user commentary on emerging stories & trends? 

It seems logical, rational & a benefit to users. It could also give publishers a much-needed path into Facebook's walled garden. I'd be more surprised if we don't see this emerge in the next couple of years.