I've posted this story before, but it's pertinent here...

A coworker used a customer's rate at a very nice hotel at which the customer has an incredible rate. Unbeknownst to the coworker, the hotel provided a list every day or week to the customer letting them know who would be staying in the hotel. The coworker's contact was told the coworker was staying at the hotel, and the contact thought perhaps there was a forgotten appointment with my coworker set for that week. My coworker was mortified when the contact reached out. It didn't take a rocket scientist for the contact to figure out the coworker was in that city to meet with a competitor. We were all warned never to use a customer's rate unless the customer was expecting us.