I stayed at a hotel in Beijing last month (I won't name which because I've been in discussion with the hotel manager about the incident and he's been very receptive to my comments). Got hit with DCC when the person who was checking me out hit the USD button without asking me. Fortunately I was vigilant, and when I saw the charge come up in USD on the receipt, I made the person behind the counter reverse the charge and do it properly in RMB.
I emailed the hotel manager with several complaints about the hotel (one of which was using DCC) and he said that the hotel doesn't control the exchange rates; the Bank of China does. I suggested that they simply stop offering DCC, since the 4.1% rate they were going to charge me was much greater than the FTF charged by the worst offending banks (which charge 3%). My card happens to charge 0%.
Why would a merchant do this by default? Do they get some sort of kickback from the bank if they let the bank rip off the customer?