Banned Performace Enhancing Drug Classes

The IOC has banned athletes from using drugs to enhance their performance. What is the purpose of this policy? Surely technology offers athletes many ways to enhance their performance. If the issue is fairness, I don't really see the difference between the new speedo swim suits and performance enhancing drugs. If the issue is athlete health, which seems more reasonable to me, I wonder what the difference is between taking carefully administered drugs and the health of young female gymnasts.
From the World Anti-Doping Agency (WADA):
"...Clean Athletes are the real heroes who make brave choices everyday by not doping. They deserve competition that is safe and fair. They deserve a level playing field."

In any case, back to science, here's a Ben Johnson's breakfast of all that you can't indulge in if your are an elite olympic athlete:
Anabolic Agents: Most importantly this includes small molecule steroids related to testosterone. These increase your muscle mass and red blood cells. Great for strength requiring events. Obviously they have masculizing effects aswell. The scary side-effect of shrinking testicles is temporary, however the long term effects are heart related and are probably undesirable. They can also make you grow a beard if your are a woman and initiate male pattern baldness early. This catagory also includes steroids used to treat asthma, Beta-2 agonists. These drugs increase lean muscle mass, and also have some stimulant properties. A therapeutic use exemption can be obtained if you are asthmatic.
Blood doping: Increasing the oxygen carrying capacity of your blood by increasing the number of red blood cells (RBCs) in your body. This is great for endurance sports. This can be done by harvesting RBCs, storing them, then readministering to the athlete before competition. This is pretty old school now and more common is the use of erythropoeitin (EPO). EPO is a peptide hormone that stimulates growth of RBCs. It has medicinal uses and therefore is cloned and available. Detection is difficult but possible. Too much RBCs makes your heart work hard and apparently if you are an elite athlete with a low resting heart rate you can die in your sleep.
Peptide hormones: There are many hormones that may give an athlete an unfair advantage. The previously mentioned EPO and additionally other growth hormones that increase muscle weight. This includes insulin, and suprisingly I didn't see a therapeutic use exception for exogenous insulin for diabetics. I assume there is.
Stimulants: Caffine is fine, but go easy on the cocaine. These increase heart rate and thereby bloodflow and increase metal alertness. I would think the most commonly used as a performance enhancer is ephedrine, mostly because I have heard about it the most.
Diuretics: Used to increase urination to loose weight. Good for being the largest guy in the smallest weight catagory. Also used to eliminate drugs from your system, ie a masking agent.
Narcotic Analgesics: No pain, no gain. But without the pain it is all gain. Opiates are probably the most commonly used to overcome injury or train for longer periods that would normally cause pain.
Gene Doping: This is the newest catagory and I don't really think there are any examples. But my guess is that you could use some techniques to genetically increase EPO or another of the above protein products in an athlete. From WADA:
"The non-therapeutic use of cells, genes, genetic elements, or of the modulation of gene expression, having the capacity to enhance athletic performance, is prohibited."
If you are wondering about your particular prescription make sure to check the complete list of banned substances from the World Anti-Doping Agency. If it's on the list, increase your dose before any competitive event, winning is everything.