It's already being done. One of my bosses recently returned from Europe (Vienna, Prague, Poland, Germany, etc.). I don't remember where, but he said in one or more of the places he visited, it is a 1euro charge to use public bathrooms. There's a turnstile and you give 1 euro to pass through. He said many people went a different route by going to McDonald's where you could use the bathroom if you purchased something and also got free wifi. So for not much more money, you got a cup of coffee, got to use the bathroom, and check your email.