I read on some MacAddict magazine that Apple got rid of their built-in mics (I don't remember when maybe late 1999/early 2000). That was just a rather unintelligent move by Apple. (The issue was the best/worst moves/products/what have you/... by Apple)
I mean, how much does it cost Apple to make one? How simple is it to use it? How many people want to use it?
Putting back the mic (as they did in the new Powerbooks) was a smart move by Apple.