Originally posted by Chasethemiles:

Same here. I don't agree with the practice but mostly I tolerate it unless I'm on my PMS. Case in point, calling a young doctor Dr. while he/she calls me by my fist name.

This is mostly a problem with U.S. doctors talking to female patients, who traditionally have been treated more paternalistically. It is a lot less common with doctors talking to MALE patients, unless they've known them for years. A corollary is where some male patients address male doctors as "Dr. ___ " but then try and first-name female doctors, especially if they are younger. There may be a little bit of a power play going on here.

This sort of thing (both in the travel business and in other settings, such as medicine) has been going on for years in the U.S. but does appear to be getting more common. Businesses think it's friendly. Most customers don't mind, perhaps some like being first-named by strangers have their age. My elderly mother, however, who was raised in Europe (where this was unheard of) is an example of someone who finds it deeply offensive, and she will refuse to answer if she is called by her first name in a waiting room, or addressed by her first name by a salesgirl.
If you don't like the practice, you can either do the same, or politely correct the person addressing you to indicate what you would like to be called. Or write a letter to customer service of the organization.