All uninformed data sales feel icky to me, but data sales that involve actual payment history even more so. There's incredible amounts of personal information int he stuff you buy for your day to day life, ranging from religious items to medicine, and coupled with an account from a party like Google or Facebook, this pretty much completely deanonimises the otherwise anonimisable internet profile.

You can get a new internet provider and a new Gmail account, but your purchasing habits won't change and are easily mined. A real-life connection between an online account and the stuff you buy in physical stores crosses a boundary that I think should not be crossed