Microsoft's second big move of the week, after Satya Nadella: investing $15 million in FourSquare

[youtube http://www.youtube.com/watch?v=DFXzyJ8mUh4&w=600&h=315]

Foursquare is still a start-up -- because it's been around for a little while, you might assume that a tech giant bought it and rolled it into their services -- and it's still raising money, including $35 million in the Series D round recently. They got an additional $15 million from Micros…