Happens very frequently in Russia and China, less often elsewhere. In Bangkok you can meet all sorts of interesting people in hotel corridors, although I've yet to have one try to come into my room. But just last week in Kuala Lumpur, staying in a very respectable hotel at that, I was awakened around 4-5 AM by insistent doorbell ringing. Still groggy, I figured it was morning already and it was my colleagues coming to wake me up or something and opened the door... only to find not one but two scantily dressed ladies at my door. They were as surprised to see me as I them, but I told them they had the wrong room and closed the door.

Speculation at the breakfast table that morning was mostly centered on what sort of person feels the need to dial up multiple escorts at 5 in the morning, and whether their bill was prepaid...