Flint said:
I don't know. People are silly and fall for the "more is better" thinking.
If you give Joe Sixpack the options to have 5 speakers and a subwoofer or 9 smaller speakers and a subwoofer, I think he will chose 9. He will probably setup the processor wrong so he can always hear the overhead speakers to make sure his investment was worth the effort and cost, but he'll choose more every time.
My experience is that you're spot on!! A partner in the A/V store I worked for left his "calling card" whenever he went to a customer's house to help with anything by setting the receiver to "All Channel Stereo" because "that way all the speakers work".
In their demo room, I once spent two days getting it set up where it was actually a decent 5.1 system with properly calibrated tone matched speakers, etc. This guy comes in and listens and get pissed that it's not 7.1, despite the fact that have the speakers in there to do that. I tried to point out that the other speakers were ceiling mounted almost directly over the listening location and weren't anywhere near tonally balanced to the other 5; therefore, adding those two would make the room sound worse. His response was, "yeah, but then we'll have 7.1".
John