WHY do people not know this???
its CLEARLY documented in the tiny manual (its about 5 pages long!) and there are hundreds of threads on here about this. search please!
People don't read manuals? Shocking!
And for the record, I didn't know about the single speaker either, but a quick call to 1-800-MY-IPHONE cleared that up for me. Oh, and I did read the manual when I got it.
And BTW, I decided to take a look, and I can't find any info about the speaker/microphone in the manual that came with my iPhone. Are you talking about the 22 page fine print iPhone manual, or the Finger Tips manual? There is no tiny 5 pager in my box. Where is it "CLEARLY documented"?