Does host need to tell dinner guests to wash their hands?

The problem: When I entertain, I always provide a generous supply of guest towels in the bathroom. However, after the event, it looks like few or none have been touched. I wash all of them, but wonder who didn't use them and how did they dry their hands? I thought of putting up a sign reading, "Please use the guest towels," but thought better of it.

Low road: Remove all towels from the bathroom. When guests come out, rush over and thrust one into their hands with your deepest apologies. Guests with clean hands will be grateful. The others will likely take the hint and make a beeline back to the sink.

High road: I'm guessing there's a subtext to your question, which is understandable for a host: Are they washing their hands? You want to resist positioning cameras at the sink or placing a sentry at the door checking hands for cleanliness, because neither option seems terribly festive to me. But you can make the hygiene habit more likely. I have a hunch that people prefer to use soap dispensers, instead of soap bars, the latter requiring one to dip into a typically soupy communal soap dish. So buy a pretty bottle of the stuff and position it near the faucet. In terms of how (or if) they dry their hands, it is possible that your guests are using the towels, but lightly, so that they don't get soggy. Or they're using their pants. Or they're shaking their hands dry. Or, yes, ick, not washing. But while you can lead a guest to water, you can't make him use it. Lessen your hand-wringing by avoiding a post-party analysis. And, just to be safe, keep the guests out of your kitchen.