Oh yeah, that makes sense. Thanks.

Ok, so we have a timestamp. What else? Because timestamp manipulation wouldn't add up much. A set of state of the art rigs and we loop through 2^32*timestampMargin in no time. So when mining equipment gets better and difficulty goes up we end up in a situation where mining success = who gets a valid hash submitted first?

Can you explain this further? I have no idea what you were trying to say with this.

50GH/s Butterflylabs' rig could run through every possible nonce in 100ms. If so what's the point of it? What makes getting a valid hash so difficult? Is it because most of the time no valid hash exists for current input data combined with every possible nonce? Or what am I missing?