Yup, I know someone who's job is doing a lot of refunding of these transactions. The offending apps are well known, he even pointed out a couple apps on the top downloads. The developers (and apple) are the ones that pocket the money
I don't know of any other addon that will sync between different browsers, which can be useful even on the same computer. I don't know why there's an outcry however when the addon tracks browsing usage by default. It's bad enough that there's no bookmark addon that I know of that allows backing up to a custom server. I gave up on xmarks when it corrupted all of my bookmarks, and upon disabling it I found firefox's memory usage dropped by around 400mb. Good riddance.