Ah, the classic confusion between "affect" and "effect".
Very few people seem to be able to tell the difference anymore. Even I sometimes forget that, albeit rarely, "affect" can be used as a noun and "effect" as a verb. I never use them as such, so I generally just think of "affect" as a verb and "effect" as a noun. I'll have to start looking for occasions to mention how something or other has
effected a change of some sort. ^_^
On the other hand, I don't think I've ever gotten into a debate over "complementary" and "complimentary". The difference between the two seems pretty obvious to me, but I guess I can see how people would get them confused. Come to think of it, I can't remember ever having seen one of them used incorrectly, while "affect" and "effect" are switched all the time. Then again, the latter two are much more commonly used than the former.