My personal favorites that make me chuckle are valid victorian, pre-madonna, pocket presents, and escape goat. Homonym misuse simply shouldn't be an issue in the 12-and-above crowd.
As for those who are so offended by corrections or even a discussion of the issue at hand, I leave you with a thought from one of my favorite professors at UT:
"To misuse one's native tongue is to be openly disrespectful of one's own upbringing, culture, and homeland. It speaks poorly of family, as good parents would have corrected it; it speaks poorly of education, as good teachers would have stamped it out; it speaks poorly of employers, as good employers would see it as a sign that shortcuts and inaccuracy are acceptable to the worker. A person's proficiency in their native tongue and the choices they make in how seriously they treat it may not be the true judge of their worth, but it's a good sign as to whether or not digging deeper is worth the time spent when time is an issue."
To use the argument that this is a message board and not life is a very interesting comment; as language is both one of a person's longest-held and least-thought-about skills, what you see written in posts is indicative of their base skills because it is often done solely for the dissemination of thought without care as to the quality of the delivery. Or, in layman's terms, what you see is what you get.