You don't need to be a rocket scientist to know that liquids and laptops don't mix. Still, everyone gets thirsty. A very common form of Mac damage happens when someone spills just a little bit of their drink on the top of their computer. It seeps into the keyboard in kills it.
A bunch of years back, this was an annoying thing to happen, but it wasn't all that expensive. Apple's PowerBooks and iBooks had keyboards that were pretty easy to remove. And they were comparatively cheap. A small screw driver was all you needed to remove the old keyboard and install a new one.
Then the MacBooks came along. Apple came up with a way to make them even thinner and lighter and more rigid. This came at a cost, the keyboards became integrated into the top case of the computer. So to replace the keyboard, you had to replace the top case, keyboard, and trackpad. A much more expensive part, and also a lot more complicated to install.
Apple's current line of laptops are all what they call a "Unibody" design. On all older laptops, the bottom of the computer was the main structure of the computer, and everything bolted to that. Then you bolted the top case to the bottom and there was your computer. The new Macs are all reversed. The "Unibody" top case is the primary structure of the computer, and everything bolts to the top case. Then a thin cover just screws to the bottom to close it up. This new "Unibody" design makes the laptops even thinner and lighter, but more noticeable than that, the new Macs are extremely rigid. The main frame of the computer is a single block of CNC'd aluminum. The old ones were thin layers of aluminum welded and screwed together. The new laptops don't bend and flex and creak when you pick them up.
But the down side, and the point of this article is: they keyboards are not easy to replace. You're not just replacing a top case that bolts to the main structure of the computer. The new top case IS the main structure of the computer. This makes it even MORE expensive than before. But the big catch is that to replace it, you have to strip every single part out of your Mac, and put it all together in the new top case. It is the most complicated procedure there is. Any other part, even replacing the screen, can be done with fewer steps than replacing the keyboard.
So as a public service announcement to all owners of "Unibody" style MacBooks and MacBook Pros: Please be extra careful with your beverages! A tiny spill can easily cost you $500 or more to fix.