Players in survival are unable to sleep when there are others in spectator mode. I would expect that they would be disregarded, however they have to leave the server in order for players to sleep through the night.
Although I think it's fairly self-explanatory, I'm apparently supposed to put step by step instructions of how to replicate.
1. Have multiple people on a server.
2. Have at least one player in survival and one in spectator.
3. Have player in survival attempt to sleep.
4. Find frustration in the fact that he can not.