I wish people would stop saying this kind of thing,it is totally impossible to get true random numbers from any form of deterministic mechanism,and the scheme which eric is suggesting is deterministic.Randomness is a very strange and the underlying mechanism is far from understood,the only source of true randomness occures deep in the sub-atomic structure of matter and nobody really knows why.
Given enough information about any deterministic mechanism,such as erics,you can always work back from any point in time and end up at the starting point and predict with an arbitary degree of precision the output at any point in time.The whole point about a natural source is that you cannot given any amount of information about the system predict the output at any point in time.