The article's central premise is that the items purchased provide unique fingerprints to identify a person. As I understand it, the study used cc numbers to link records to build their system, then once it was built, they could use shopping habits solely.
Sure, I'd much prefer 1-1 sessions rather than a group meetup. Don't get me wrong -- the meetups are great, and it's fun to meet new people. But you don't get to dig into much of anything.
I'm in SD (live in PtLoma, work downtown) and am down for a cup of coffee or lunch. Can do during the week if it's close to downtown, otherwise I'm sure we can figure something out. Email is in my profile.