To add a little balance to this discussion, it is worth noting that whilst Hamilton does push his luck quite frequently, he is not the only driver who has pulled some questionable moves.
For example, in the wake of the Malaysian GP, Kubica was asked what his opinion on the Hamilton-Petrov incident was. Naturally, he was critical of Hamilton, saying that his move was "a Formula Ford thing", but then went on to say:
Robert Kubica wrote:"I think there were too many moves during that race - not only from one driver. I don't think it was only one driver who did more than one move. It's important that you don't move when you are side by side."
Full article here
http://www.autosport.com/news/report.php/id/82875So, although Hamilton is the driver who has the most aggressive attitude on the track, it does seem that there are some drivers who are getting away with questionable moves because they aren't caught on camera (I guess that you could push you luck a bit more in the mid field because the cameras tend to focus mostly on the leaders).
Equally, Hamilton coupled that statement on the stewards with another statement where he said that he intends on backing off a bit on the confrontational style that he has, so although he may have been quite aggressive up until now, he may start to reign in those antics. Whether he does so is another matter...
As for the stewards, they are in a difficult position. Their primary role should be to ensure that the regulations that are set out by the FIA are observed by all parties for the safety and benefit of everybody. From that viewpoint, they should be strict with their rulings, which should act as both deterrent and punishment. It can certainly not be denied that Hamilton has been involved some moves which have crossed the boundaries of what is and is not acceptable.
What is more problematic are the moves which sit in that grey area between what is and what is not acceptable, where he might not technically be breaking the rules but is pushing the interpretation of what is and is not legal. From a regulatory view, you would probably want to take a harsh line to prevent people from abusing the regulations, since your overarching priority is going to be safety.
On the other hand, we can see that there is a competing commercial interest. The general consensus amongst fans is for more action on track, with drivers racing wheel to wheel (coming back to that gladiatorial element which others have alluded to), and controversy on the track means more publicity of the track in the sports pages and websites. After all, Bernie is revelling in the recent antics of Hamilton, saying that he has loved his recent performances on the track and thinks that the others should, to quote the man himself, "stop complaining and get on with the racing"
http://www.f1technical.net/news/14683 The very fact that we are currently sitting here discussing this must be music to Bernie's ears, since we are ultimately helping him to drive the F1 press machine.
So, there is a conflicting pressure from FOM to be lenient on the drivers to encourage them to go for more aggressive and bolder passing manoeuvres. After all, Hamilton has currently racked up 32 overtaking manoeuvres in four races, and it is true that at times he has helped liven up what could otherwise have been dull races. Equally, the fact that he has been so eager to push on and pass people has helped Mclaren out - after all, they now lead the constructors championship thanks to the 1-2 they got at China - and there have been times when the team has been just as involved as the driver. To a certain extent, they are going to want Hamilton to keep on attacking, even if it doesn't win them any friends, because their ultimate goal is to win, and sorting out the arguments can always be done later.
And there is a bit of a vicious circle here - if one driver pushes the rules, and gets away with it, then sooner or later others will continue to push the rules in order to try and gain an advantage for themselves, which in turn tends to encourage drivers to bend the rules.
Remember Hungary in 2003 (I think)? The track owners added a tarmac run off area for the exit of Turn 1, and soon enough, some drivers chose to use it to widen the corner entry and take more speed through the corner. Whilst technically they were breaking the rules (which state that you must remain within the boundaries of the track), soon enough all of the drivers were doing it, even though the GPDA had originally told the drivers not to do so.
As a result, I would not dismiss the possibility that Hamilton (and others) will get involved in more trouble with the stewards - and equally, that the stewards may be pushed by Bernie to take a more lenient approach.