This really doesn't change Apple's policy towards warranty repair. Basically, it's the same as always- misuse your Mac by getting the internals wet and toasting your motherboard is not considered a manufacturing defect.

Auto manufacturers work the same way - ingest water into your car engine? Don't expect a gratis replacement.

Of course, incidents do happen, and there are third party insurance programs that cover losses like this.

May we bid a not-so-fond farewell to the "water damage" claims - against people that followed directions and cleaned their screen with a commercial moist cleaning pad - because a bit of residue could be seen on the outside of the display bezel.

Why not try to waterproof the laptop? It isn't like spills into laptops are anything new. Apple should be a leader and spill-proof their laptops instead of adding moisture detectors.

How about the use of it in a Really humid country like Panama, Singapore or any tropical like climate where humidity can get up to 80 or even 90%?

How about when the sensor detects a spill, the camera takes a covert picture of the panicking person with a tipped over coffee cup? ;-)

Seriously though, waterproofing a laptop is done. Ruggedized versions usually are. Do a search for the cost of these though and you'll see what it isn't done in general. If you drink near your computer, keep it in a spill resistant cup and be careful. If you eat, well, just don't eat near your computer. I hate going to someone's crumb laden, disgusting keyboard. Take a break and eat at a table.

I hate these things. My Samsung Blackjack II stopped working and I took it in to at&t to get it exchanged, but the detector had been set off.

I never spilled anything on my phone or got it wet. I had been in Houston during a particularly hot and humid time when the phone stopped working and I asked them if the phone being in my pocket for several hours in a humid climate could have caused the wetness sensor to be tripped. They said it was a very likely possibility. Ridiculous.

Instead of using this sensor solely to give Apple an excuse not to provide warranty repair, why not use it to prevent damage in the first place?
Could it not be implemented to cut power to the computer immediately upon detecting moisture?
I would think that in at least some instances, this would prevent damage, and protect the user instead of just Apple.

The idea is fine. However, it's probably a chemical sensor, not an electric sensor.

While there are cases of accidental tripping of the sensor, it's far more common that people spill stuff and don't say anything when they send it in. However, it's usually pretty obvious if they spilled anything but pure water on the system.

The idea of using these sensors to cut power to the machine is flawed. First off, the cost would be much higher for an active sensor than the cheap ink dots that they currently use. Secondly, the placement of the sensors will not detect moisture unless it happens to hit the sensor. It's certainly possible to damage the computer without water hitting the sensor directly.

how do you waterproof something that needs ventilation?

a low power rugged notebook can be reasonably waterproofed, but not something as full-featured as a macbook. ports, speakers, mics, cameras and fans! you want the fan to circulate water as well?

good luck with that.