Auto increment is a no-no?

Hello. I must confess that I am rather new at this. During my courses, I was taught to place an auto increment as an id field in my tables, when in need to.

However, recently, I heard someone comment that this is to be completely avoided. But I do not understand why. Perhaps anon could point me in the right direction?

>>4
I know. Thus, I ask. Auto increment gives me an unique id for my rows, but for some reason I do not know this is an incorrect approach.

Why?