if Amazoin or someone decided to use a few of their many datacedntres just to generate bitcoins, what's to stop them cornering the market?
Anyone who owns a large proportion of Bitcoins (say, more than 1 million) could in theory corner the market.
But that would be a one-off. My estimate is that you could permanently crash the price by selling 1 million BTC at once. But then you would no longer own 1 million BTC, and the price would eventually creep back up
as more users join. Somebody actually
did try to crash the market by dumping 30,000 BTC back in September. They failed - the price went back to the original almost immediately.
Also, no matter how many datacenters you fire up, you can
at most generate 7200 BTC per day. That is hardcoded into the protocol. So, to get hold of 1 million BTC, Amazon would not only need to fire up the equivalent of several supercomputer clusters, but keep them running for several months. Even a large company like Amazon would have to justify that kind of investment to its shareholders. They wouldn't do it for frivolous reasons.
And what would 10 bitcoins buy me, how many British pounds for instance, could I buy with a bitcoin?
There price of Bitcoin is free floating. Currently it's trading at approx. USD 0.25 / Bitcoin.