I am not going to argue about it.
But just for reference, are you talking about with or without headphones?
I tested it today without head phones, and when I turned down my iPod, and then pressed home, and then went in to settings, my ringer volume was down and not on full like it was before I started the process.
Then I went back to iPod, turned the volume to full blast, and went back to settings, and my ringer was at full blast.
And I know for a fact I am not the only one that has this complaint about iPhone 3G. It is WELL documented.