I lived in $nowheresville, TN for a bit. This drove me insane. Sure, your webapp works great in downtown SF, but try loading it with the spotty connection the rest of the country has, not to mention the rest of the world.

One of the places I worked at had a computer hooked up to a ~800 kbps modem, and would test all their web-pages on that. It was really eye-opening, and I wish more companies would benchmark like that