Ha, I had a couple of experiences alike also. But then if you look at the big picture, it makes sense. You're a solid target for Bitcoin ads, you're in the same location with 3 other people, likely same demographics, interests, social status etc. and they become a target too?

This is all suppositions of course, I have no idea how it works. But I've tried this experiment with my gf once:

We both opened Instagram and started talking about a product class that we never saw ads for there, say like shampoos. We even mentioned a few brands and then waited for the ads to hit us. They never did.

EDIT We use iPhones