An older excellent article on the prevalence of Arial on computer desktops and a sidebar which shows typographically challenged designers how to tell Arial from the typefaces it was designed to imitate.
“Arial’s ubiquity is not due to its beauty. It’s actually rather homely. Not that homeliness is necessarily a bad thing for a typeface. With typefaces, character and history are just as important. Arial, however, has a rather dubious history and not much character. In fact, Arial is little more than a shameless impostor.”
Read: The Scourge of Arial and How to Spot Arial