One word..... WARRANTY! People get crazy with tune, lean it out (especially with forced induction cars) blow it up, remove the tune, take back to dealer and say my car won't run......
I have even heard that manufacturers have watched forms and found people's modifications or found videos of racing, and void the customers warranty. Read a thread on a Subaru WRX forum, the guy even posted a letter from Subaru showing why they voided it. Take it for what its worth, it is the internets.....

 

Good points for sure, but a tune from a reputable company is not going to blow up the engine. It will only make it run more efficiently, and on similar throttle, it will get better gas mileage. I am going with a supercharger, and have no illusions of warranty coverage on engine-related failure, although I will have a warranty from supercharger installer in case anything catastrophic happens. Just do research and be sure you are getting quality components for your $40,000 vehicle -- there is a lot of talk of saving a few dollars with Home Depot intakes and chop shop exhausts, so just be careful. I have modded every vehicle I have ever owned and never had an engine issue -- twin turbo Supra, blown Miata, blown S10 Blazer, blown FJ Cruiser, 500 hp G8, and a supercharged V8 Solstice (my favorite). Just know what you are getting into and enjoy the added performance.

 

True, the key being that the tuners know their stuff. I agree on not cutting corners. What the manufacturers can not control is IF the customer puts a good tune on it. If the customer gets a bad tune and hurts the motor than the dealer is left with out of pocket repairs when there was nothing wrong with their product. I am sure that can end up being a nice amount of money. Not the case for the HEMI, but I also think that manufacturers are pushing the edge (HP) wise for long term durability on stock parts. Look at the HP numbers on the new 5.0 a lot of the mustang guys are seeing dyno corrected numbers in the 420's from the wheels stock. Same way with the new V-6 eco boost. A lot of the Ford guys are saying it is pretty maxed out. I think it is a big picture thing, you make more HP you create more heat, now can the cooling system handle it? Can the fuel system support it? A good tune does not elimanate parts failure due to exceeding design limits. It is a domino effect. I am not referring to adding 10 HP I am speaking of more so a power adder such as forced induction.