I'm sure I'm going to have to hide this thread at some point 
I work in racing, though my job is more Flat orientated, so am happy to answer any questions that people may have.
What you have to remember is the sheer number of racing that takes place in this country. There are over 17,000 racehorses in training in the UK at any one time. In 2011 this amounted to over 90,000 runs, that is to say some horses raced once or twice, others 8 or 9 times. The recognised fatality statistics for British racing is around 1.6 per 1,000 runs. This compares to 2.4 in the USA. The facts and figures are out there, they are not hidden away you can find them all on the British Horseracing Authorities website.
Every fatality is a shocking loss to all connected to the horse, but you cannot eliminate 100% of the risk in anything. Take the example of a horse that sadly died at Aintree today - Gotany O's. He took a bad step whilst racing on the flat (ie he was not jumping a fence at the time) and broke his leg. This could have happened to him at home or in a field, it was a tragic accident.
Racing is not cruel to horses. They can, and often do, refuse to race. The use of whips is highly monitored, we have some of the harshest rules in the world on this matter, but can I ask how many of you have seen a racing whip? The are completely different to normal riding whips. They are heavily padded and bend a great deal - it is almost impossible to get any force behind them, so to say horses are beaten is an outright falsehood.
[dons flameproof suit]