One of the inherent risks of having an iPhone will necessarily mean that you will become a de facto sales rep for Apple.
It's not uncommon for co-workers, non-iPhone-laden friends or strangers asking to 'see' your iPhone. "See?" Is that the right word? No, perhaps play and fool around with your iPhone is a better description as you can plainly see an iPhone, but these people clearly want to touch it to believe it as the Apple ads direct them to do. It happens to me enough to make me feel like a roving iPhone sales rep. Steve Jobs should cut me a check! (Note: store credits will not suffice!)
Anyway, I typically oblige and don't mind showing people the iPhone. My first thought usually focuses around potential theft: it's not like they're going to run off with it, and if they do, I'm pretty sure I can catch them. But, my second thought I have as soon as the iPhone actually leaves my hand, is: what is exactly pulled up on my iPhone? What was that site was I just looking at? What was that last SMS text message I just got? What if that message was from that special somebody (or somebodies?) What was the last picture I just took? What was that email I just got? Not realizing what these may be, I usually quickly exclaim to people not to look at my SMS text messages and/or email. But these are the touted features of the dang thing, so usually, I'm a little more tactful about it and offer to give the would-be gawker a "guided tour" of the iPhone and its features. If I'm not lucky enough to get the iPhone back I nervously wait.
I suppose this is part and parcel to why having a passcode on your iPhone is a good idea. I've talked about this idea before and, now note, that having the passcode is a pain in the a** sometimes especially if you're listening to the iPhone's iPod and want to change songs, or rapidly respond to a SMS text message. But here, it's a little different. I doubt that you're carrying around state secrets on your iPhone (corporate data may be another matter) and here, you're not worried about your iPhone falling into the wrong hands. But what I'm talking about here is that the "enquiring minds want to know" mentality. My friends with iPhones have observed the same thing too. If we were famous, our iPhones might be a paparazzi partisan's dream. The New York Times even wrote an article about this notion in general in an article about spying spouses snooping on their significant other's computers.
All of this perhaps makes the "restore" function even more appealing. Wiping out the iPhone's memory all away may be nice because of the very public nature of a device like an iPhone containing private personal information that you might want to keep away from would-be looky-loos.