> They're selling your personal check-in data to retargeters
There's no evidence that that's happening.
According to Foursquare's pitch deck, that's exactly what they plan to do.
Cite it, then. I went through the slide deck. It talks about aggregating and selling "retargeting personas" based on check-in markers (e.g. "checked in once at a resort in the last year"), but nothing about selling your personal check-in data.