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?

>>10,11
No shit. (Warning: suspicious use of specifier 'conversely'.)

>>12
I could circuit the Earth without having someone need an SQL database. 99.98% might think they need one until they see the DBA rates, then they will listen to reason when you offer a better alternative solution. (Example: No one using MySQL needs SQL. If they did, they wouldn't be using MySQL.)