Here is an article from MSN Lifestyle that is an interesting read.
I was unaware of a couple of types of travelers, especially the begpackers - young tourists who show up with a backpack and not enough money to cover their trip and busk or beg to support their traveling. I hadn't thought of bachelor or hen parties as being a travel thing. I can certainly understand why they wouldn't be greeted with open arms. I know rowdy sports fans from other countries can be a problem as well.
Daytrippers and cruisers are mentioned. It sounds like Venice gets a double whammy.
The other interesting category is groups. Amsterdam is limiting large groups within the city and banning groups from the red light district. The good news is that the smaller Rick Steves groups will probably still be welcomed.
I guess we have been lucky to have traveled to major areas before the huge tourist boom. We no longer feel compelled to see the big sites and can avoid the crowds and still have a great time. We are also able to travel during the shoulder and off seasons. As a couple we also travel "low to the ground", staying in more modest (and interesting) accommodations and not moving from one location to another every night.