and so on...
Named because it sounds like and has a similar rhythm to firing an automatic weapon. Usually not that annoying, but can be incredibly irritating when done by that lazy co-worker always slacking off at work or that college roommate that IMs until 5am every night.
Also known simply as "machine gunning".
Coworker 2: "I'm really busy right now. Kind of overwhelmed."
Coworker 3: "Bullshit! All you're doing is IMing your friends. It's pretty damn obvious by your constant machine gunning. Now do your frikkin' job."
I really needed to crash because I had the spins from partying too hard, but I was kept up all night by my herb of a roommate machine gun typing to girls he'll probably never meet in real life.