Another scam is to present your CC bill from the overseas hotel with the charge already converted into your home currency.
Last month I was at the IC in BKK and was presented with a bill for about GBP320. I insisted on paying in Baht but retained the voided charge sheet for interest, to see what the GBP charge on my credit card statement would be.
Answer - a whopping GBP20 less! Now that is using a Nationwide credit card which does not have loading fees and the exchange rate is very good, but none the less a big enough difference to pay for a return limo transfer to the airport.