|MadSci Network: Medicine|
To answer your first question, according to the National Center of Health Statistics, there were approximately 265,300 appendixes removed in 1996 (http://www.cdc.gov/nchswww/data/ad301.pdf). 1996 is the most recent year for which statistics are available. To answer your second question, a person will have their appendix removed if it gets infected. Since the appendix is really a small, finger shaped pouch off of the intestine, it is very dangerous for it to become infected. If it does become infected it can burst, and the bacteria inside the intestine can escape and infect the inside of the abdomen and/or other organs inside your body. When a doctor suspects appendicitis (the infection of the appendix), she will immediately perform surgery. About 15% of the time the person's appendix is not actually infected (Beers,MD, Mark H. Merck Manual. Merck Research Laboratories. p.265), but it is better to be safe than sorry.
Try the links in the MadSci Library for more information on Medicine.