You're new to Hacker News, but you're encouraged to 'show your working' here along with your comment.

I welcome to see the data that Square is tracking purchases, and if it is, how is this any different to XYZ Supermarket's loyalty program/card, and how are they doing this without breaking any laws.

(Oh, and they've handled $15bn in transactions, sans Starbucks, I doubt they need the moolah!)