I've had some bad hosting experiences as well - but amazingly few, considering how many people we've been hosting.

Sometimes the chemistry simply doesn't fit. One thing I dislike is people that are just considering such offers as free lodging, an alternative to staying in a hotel. We've had guests we haven't even been seeing - sleeping when we go to work and coming "home" after we've gone to bed.

Some of those folks also make efforts to "disturb" the host as little as possible, if they get a room allocated they stay in the room, they don't participate in our meals but make their own meals instead, without sharing.

Sometimes we find that we simply does not like our guest, for various reasons. It's OK when the guest is staying only for some few nights - but it's horrible when we've appointed that the guests should stay for for several weeks and we learn on the first day already that we really don't like this person. Even worse, having ... ahem ... homeless people that have no plans on what to next, where to go or when to go. I think once or twice we've had to ask a guest to move out. We have had guests staying for more than half a year, it works out if the chemistry fits.