One time my brother found a fraudulent charge on his credit card from Guitar Center and asked if it was me. He was concerned it might have been because I used his computer once, I had an education in IT, and that I play guitar. I would never do that to anyone, let alone my own brother. I told him no, but he still thought it was probably me. That really hurt. He did some digging and found out the guitar had been shipped to an address in a completely different state, so that was proof enough to him that it wasn't me. He then apologized for accusing me.
Another time I was sleeping and my dad woke me up all urgently and said he just stopped a $400 something charge from Amazon going through because my credit card (under my dad's account) had been compromised. I was like "no, that was me, I just ordered my text books for the upcoming semester. Didn't I tell you?" I thought I told him I ordered them but he said I didn't tell him. Oh well.