Howzit

For technical details on how EPO works, a simple type into google will provide more than enough info.

With cycling, a different dynamics here are a few thoughts.

EPO is regarded by many pros in the peleton as "healthy"
Yes, healthy.
Why?
Well simple. At an average of 45km/h for 3 weeks, potatoes, peas and carrots, washed down by water isnt going to leave your body in any good shape. Your career will be shortened and you will be a leathery old man by the time you are 35. Some riders consider EPO as a "strengthener". A tonic that merely helps you recover to go race for weeks on end.

Honestly, I agree with this sentiment. See, when you train and race daily, your natural himatocrit levels go down. If you are racing at Grand Tour level, they (red blood cells) will deplete until you are in hospital. Unless you are allowed some weeks to do nothing to recoop (which you wont, because if you do, they will give your contract to someone else), you will get sick and over train. This is science. It is simply what it is.

The simple rule of 50% in my opinion was a safety measure to keep the riders from over doing it, and was enough to allow riders to race year-round without becoming ill or over tiring their bodies. Unless we all decide that the Tour should only have 120km stages, it is simply unhealthy for any human to do the Tour at the distance and intensity required these days. The 50% rule was fair, healthy and safe.

The biggest blunder that the UCI could have done is getting a test for EPO. Now riders resort to blood transfusion. A FAR, FAR more dangerous activity. Its such a pity.

In addition, training at altitude is the same as taking EPO. Sleeping in an altitude tent is the same thing. So are both of those illegal? Why not? Further more, there are people like myself, born, raised and trained at 2000m above sea-level. My parents, grandparent all grew up at 2000m above sea-level. Look up Kenya and other such countries (im from Zimbabwe).This means that my blood will have different characteristics from those born and raised at sea-level.
In fact, the UCI had special exemptions for such events. Some riders were allowed a 52 or 53% rule.

Ultimately, unless a rider was on 65%, there was no real benefit for a test other than the 50% rule. The only difference is that in some instances, like the columbians, and other ethnic races have larger red blood platelets by nature. This means they may have a naturally lower level (red-blood cell count) while living at altitude, but when you boost it up to 50%, you have a greater advantage than Caucasian athletes for example. This has been attributed to some of the success that the Kenyans have had.
Of course since cycling is an endurance sport, you will never get ride of blood manipulation. The best thing you can do is CONTROL it. Thinking you can eradicate it is arrogantly stupid.

Even now, they think they have a test for EPO. What fools. The test can only detect EPO that has been injected over the last week or so as far as I know. EPO takes almost a month to take full effect or to boost you up to where you want to be. (One injection every week). One can easily boost their himatocrit in winter, give yourself 2 weeks, after the last injection, then draw blood packets to store. Use them during the season, and you cannot detect EPO. This puts the riders in far greater danger than the mere 50% rule. Where riders only have to take EPO and avoid the whole blood storage, transportation and re-infusion of blood.

The issue of EPO is far more complex than one might initially think. But those are a few things to think about.