Oh Uber absolutely does this! I drive for them occasionally, and sometimes I'll see price hike a little and not for very long. Then I tried to use it one time drunk at a bar ~2 miles away. Checking back and forth for about an hour or went from ~$70 to ~$30. And shocker, the driver said he was only getting a few bucks on the surge premium.

I once bought a couple copies of a book as an inside joke for a couple friends.

It was not at all a popular book, I can pretty much guarantee that you've never heard of it or it's writer, and odds are you'd probably hate it if you did ever read it.

I think when I bought them they were going for about $5 a pop.

And immediately after I ordered them the price shot up to like $15

I can only assume that the algorithm assumed that something happened that made that book popular all of a sudden, instead of just one asshole buying a couple copies to give to his asshole friends as a joke.

Took a few months before the price dropped down again.