My admin spends a couple of hours a month reconciling credit card bills to receipts. We find $100 - $200 a month for miscellaneous charges that we didn't make. When compared to our $40,000 a month of expenses it isn't a large amount, but it shouldn't be happening at all. Typically it is a dollar or two on a hotel folio, but we once had a $1,000 charge from a hotel that no one could explain. Honor bar charges are frequent. We have a company policy of not accepting the key to the honor bar, but we still get the "you must have bumped into it" excuse.
The most flagrant one was from United Airlines. I tried to open a checking account and was told that I had an outstanding hot check to United Airlines. I spent hours trying to find out what it was only to find out that a ticket agent had written a peroneal check, put my ticket number on the check and apparently took the money out of the cash drawer. When the check bounced United charged it back to me. Of course the check was in their ticket agent's name so I was never notified. It took months to clear it up.