So back in Idaho, I took my bike into a bike shop to be checked out as the drive train was making a little noise (Jason needed some loctite on his jockey gear bolt). I suspected the crankset (the axle bearing system), but I have no real way to get in there with the tools I have (I would have to carry a lot more tools to be able to do crankset work, and this stuff never really fails catastrophically anyway). The guy told me that everything was fine except that my chain was way too grimy and had gotten stretched. His gauge essentially said that I was past the point where simply replacing the chain was possible (essentially, saying that the chain and the rear sprockets would both need to be replaced at once). This made me unhappy, since I thought that I had been keeping good care of the chain and was making sure that I would replace it before it got too stretched. He suggested that I just ride it till it breaks, then replace the whole drivetrain. (For those not in the know about drivetrains: The chain will stretch and wear over time, and will also eventually start to wear down the teeth on the sprockets (front and rear). The best thing to do is to replace the chain when it gets a little stretched (since this is cheap), thus saving the wear on the sprockets. If you wait too long and the sprockets get worn down, then a new chain will not be stretched enough for your worn sprockets, and the chain will slip - thus you have to change both the chain and sprockets (which costs more).
But today we are in Whitefish, Montana, just outside of Glacier National Park, and we stopped at another bike shop, since my drivetrain had been making increasing amounts of noise (new, intermittent clicks started to appear 2 days ago, and have gotten stronger with time). The guy said he was pretty sure it was due to a loose crankset. He also measured my chain and said that it didn't seem too worn to him. I had him disassemble/regrease the crankset and change the chain, since this was due soon. In the end, the reassembly of the pedal bearing got rid of all the noise, and the new chain doesn't slip at all on the existing sprockets, so the chain was not too worn either. 2 points for eric.