The difference for me between the scenario of Senna potentially leaving McLaren in 1993 and Hamilton potentially leaving McLaren in 2009 is that Hamilton owes his entire career to McLaren (and to an extent Bridgestone) whereas Senna was expected to go where the pace was and McLaren were aware of this.
Your correct but and Mclarens money certainly helped.
But he has talet and would still of made it without them.
The fact is Mclaren is a business and they invested in Hamilton, and got a WDC out of it.
And would of got a WCC and WDC in 2007 if it wern't for a stratagy mistake in China and a Driver/Car Error in Brazil.
And they still get plently of sponsorship money from it.
In Summery what ever they paid in to Hamilton to get him there they have got it back.
You could argue that if they had got Pedro or Parfett and Alonso in for 2007 and kept hamilton as a test driver they would of a WDC and possibly a WCC and the same in 2008 from Hamilton or Alonso and no fine.
Hamilton has said "i'm happy where i am" although he was abit quiet regarding his contract and if he would stay for 5 years.
But i think its a case of him feeling abit let down by Mclaren because he did somthing they told him to do and he got called a liar which is partialy his fault for doing somthing he knew was wrong but its also the teams for suggesting such a stupid idea.
But out of all the other drivers in the F1 field today i'd perfer Hamilton over them in Mclaren even because hes one of the best and most consistant.