I was fortunate enough to be able to go on an overseas trip to China during my first college summer break. The phone and Internet service was spotty, but I was too busy exploring to care. When I got back home, I discovered much to my dismay that my domain name had been transferred away without my consent.
As it turns out, one of my old Internet "friends" had access to an administrative account at my registrar without my knowledge. They transferred a handful of my domains to their own private account and continued to run the website as if it had been their own. They moved the database, code, and everything. (I had allowed them access to the server, so it wasn't unexpected that this was within their capability.)
Being a college kid, I wasn't able to think of lawyers or legal avenues to get it back (not could I afford them), so I wrote my "friend" out of my life and took it as a hard lesson learned about privacy and security. And trust. Definitely learned a lot about trust.
FWIW, it's still online today and probably brings in a thousand dollars a month in ad revenue.