How do preference files become corrupted? I've read a few different troubleshooting articles and Q&amp;A's where the culprit is a corrupted preference file for an application or process. Typically the solution is to delete the bad preference file and allow a new, default preference file to be spawned upon restarting whatever software was misbehaving.

How does a preference file become corrupted? Is this simply a low-level read/write error, or is there a higher level error occurring in some cases? Is it just malformed or misspelled XML? 

I believe plutil could tell you if there's a syntactical error with the file, but again, how was the error introduced? I'm unclear on the usual source for these corrupted files. Thanks.
It can be caused by a great number of things, but I believe the most common cause is where the file is being written to, and the application terminates before it's finished writing the file. This could be caused by system overheads being too great for a successful write at the time.

Hardware errors with the hard disk, or memory could also cause data errors, but I would imagine these would be the least of your problems by this time.