Hotels can be interesting. We have stopped along the road, went to the desk, and were quoted high rates. Wife goes out to the car, booked same room online for less. (she uses booking.com)

Interesting! A couple thoughts:
1. Maybe they started out with a higher “sucker” price for me because of what they know about my browsing/buying habits.
2. Maybe a machine learning program has run a 6 degrees of Kevin Bacon on you and me and have figured out this is a topic being discussed on a large-ish specialty forum. Cue creepy music here.

One woman said she got an ad for a baby stroller after meeting for coffee with a pregnant friend where they discussed that exact type of stroller. Her first thought was that her phone was listening in. But she later learned that her phone geotracked her to proximity with her friend (also geotracked through her phone) who was known to be pregnant. After they searched online together for strollers over coffee, both were tagged as likely stroller buyers. The connections spread like measles, with each new person bringing their own dataset into the mix.

Big data, anyone?

that's exactly how airline tickets work. That's why I always clear my cookies before looking for and before buying tickets.