I had my Blizzard/Battle.net account broken into - there was nothing to steal at the moment (I had played some multiplayer something a decade ago with one of the free multiplayer-only installations).

When I wanted to create a Hearthstone account, I found that out. The Blizzard CS reps were pretty decent, and they eventually fixed the issue (I still ended up creating a brand new account with better security since I was paying money this time).