Just to put my two cents in this disscussion; I tip the housekeeper daily, putting the couple of dollars on the pillow. This way, the person cleaning the room that day, gets the tip.

However, I have wondered if the "Supervisors" that come through and knock on the door to check the room, take the tip befor the housekeeper gets in to clean the room.

I tip because I am thankful for the housekeeper and I assume they are making minimum wage or below. When on business, I just consider this part of my daily per diem and do not add it as an extra reimbursable amount.

I have had experiences like other posters here, that when doing international travel, they are VERY VERY appreciative of the tip.