"Not sure how. I'm an Apple girl," tweeted one user who received the badge.
"How did I do this with a Blackberry?," tweeted another.
Others resorted to a simple "why?" or, more bluntly, "wtf?"
The confusion stems from a promotional badge gone wrong. Designed for users who check into a Windows Phone event or follow "WindowsPhone" on Foursquare, it was instead unlocked with every checkin.
Foursquare has responded to the gaffe by sending this message to recipients of the badge:
"We just wanted to send you a quick note to apologize for mistakenly awarding you the 'I Love Windows Phone' badge earlier today. Who's to say what you love, anyway? If you do love the phone, you can unlock the badge fair and square by following foursquare.com/windowsphone and attending one of their awesome events. Until then, we'll keep it out of your trophy case – and stop meddling with the affairs of your heart."
Foursquare has hosted promotional badges for everything from universities to the Jersey Shore -- as far as we can remember, without mishap.