I'm starting to hate it when I ask my students a question and they answer "Of course!" In fact it's one of my pet peeves.
Here's an example of a typical conversation:
A: Did you see Spiderman 3 on the weekend?
B: Yes I did.
A: Did you like it?
B: Of course!
This obviously is an error seeing that there was no real way for me to know their response in advance (I feel like an idiot for not knowing now).
The mistake arises from translation. "Of course" in English has the feeling that the speaker should already know the answer. 當然 (dang ran) as it is written in Chinese has become a cliche among young Taiwanese, along with the regulars like "strange" 奇怪 and "cute" 可愛.
All these expressions are overused in Chinese. Beware!