I got a message last night from a cyclist stuck between a rock and a beach. The website caused his inconvenience. Fortuantely he was only bothered by a "curious" person and not a cop (who would have put him in jail).
I received the message about 6PM. I responded about 6:15PM. He didn't get the message until the next day (today). In this day and age of instant messaging, we have come to expect that our tech experience is seemless. Alas, it is not.
So for Warmshowers to be more useful, it must advise everyone that messages may not delivered in a timely manner. A banner at the top of message entry area would be a good place. Missed communications could leave someone unecessarily out in the cold, or even jail.
Thus, again, cyclist need to contact hosts well in advance.