everybody pretty much rides when they feel like it, trail conditions be damned. you of all people should know that by now. ;)
i used to get worked up about people thrashing trails in the rain, but things don't seem to change so i've just learned to live with it. it just means rougher, more chundery trails that, in the end, keep people away.
Most of the trails I like involve a lot of pedaling, so not many people ride them anyways ;)