Facebook's hit all sorts of growth records in the last month or so, with its private stock reaching an all-time high ($65 per share) and its user count topping the 500 million mark.  Now, it looks like the organization may expand in another way, as a rumor has it ready to acquire Hot Potato.

Hot Potato is a check-in service that takes possibilities other than physical locations into account.  Users can, for example, say they're listening to a particular song or reading a certain novel, not just check in at a concert or a bookstore.

Other notable details include the fact that Hot Potato has an iPhone app, and it's also able to repost users' updates to sites like Facebook, Twitter, and Foursquare.

So back to the acquisition rumor.  MG Siegler wrote, "We're hearing from sources close to the deal that Facebook is in late stage negotiations to buy Hot Potato, the social activity service.  The deal is not yet finalized from what we're hearing, but could be at any moment."

Siegler later continued, "Hot Potato raised a small $1.42 million Series A round late last year, so it should not be too expensive for Facebook to buy such a company."

As always, we'll be sure to report any updates if things become official.