I detest them. Even at the end of the day on the more advanced terrain, when there are plenty of chairs up the hill, I prefer to ride with another person.
When the lift-lines are long, of course, everyone detests empty chairs. Empty chair means you have to wait a bit longer to get your seat and of course lift and resort operators do not like them either for the same reason. They want people to ski as much as they want to, after all who goes to a ski resort to wait in lift-lines?
However, as my opening states, even if there is a surplus of chairs, I still do not like empty chairs. When I am skiing to the chair (which often happens in the last half hour of Sunday skiing over on the advanced terrain) I will motion to the person behind me to join me up. Usually the first question is how is it going? followed by where from?, and from there the discussion goes where it may. I have met previously unknown neighbors, I have met people active in the local ski industry, in general I take an interest in everyone I ride with.
Not only does this possibly serve to liven up the ride, but who knows, maybe it will lead to valuable connections; connections that will beneficially serve the both of us. More often than not, it has lead to countless discussions. Every now and then I ride up with a conversation-challenged person. I ask a question and it is tersely answered, more often than not though, those are children or teenagers. You try.
So, when there are plenty of chairs and a skier (or boarder) beckons you to join them on the ride up join along!