I was scammed out of a huntsman knife by a guy impersonating my friend. I thought I was being careful as hell, but impersonation never once crossed my mind as something sombody could. I wasn't able to get my item back, despite chat logs and such.
I treat it as a learning experience, and I'm quite thankful for it honestly. In the end I was only really scammed out of 2.49$ and a case drop.