One thing that really makes me sad is the idea many people have that philosophy is some kind of academic discipline that needs to be studied and that you can't be expected to partake of if you're not "educated". That's exactly the opposite of what philosophy is! Philosophy is for everyone. It takes nothing more than a mind, a few undisturbed minutes and the willingness and desire to learn.
Before I go on, since philosophy is a very unclear word, I'll give as accurate and clear a definition as I can: the use of reason to attempt to gain beliefs about noncontingent subjects. (Contingent subjects are the domain of science.)
Another thing that irks me is when people seem to care what some famous person like Plato or Aristotle thought. Those guys were all idiots! You know some of the things they believed? Besides, the whole point of philosophy is that it's entirely internal, and that's why it's protected from the Principle of Contingent Uncertainty.
Then of course there's the omnipresent idea that something other than philosophy is able to trump it. This crops up whenever someone responds to my a priori arguments here with "But it's been scientifically proven!" It doesn't matter what other evidence you have; if there's a logical contradiction in a belief or if it goes against the directly experienced nature of the human mind then you know it's false, period. You might as well say it's been scientifically proven that there's a number that doesn't equal itself, or that humans really only have two emotions and there's no difference between sorrow and anger.