I just thought this very same thing earlier today. And it's just not limited to silverware. I very often think off how many people have done the same thing before. That's not so nice thinking pattern in a public toilet.
I know who uses my silverware! And if they are eating in my home, well I approve of them putting my silverware in their mouth. And I'm ok with putting the silverware in my mouth that they used after I washed it.
Hey, I'm not saying that this is at all logical...just that it freaks me out.
For some reason, they freak me out.. essspecially the ones with funky features like their face was meant to be unisex/confused looking.. I don't know how to describe it, but I did a photo project on one, and it turned out pretty neat..