Probably depends on hospital, my local private one has rooms with just 2 beds but others have up to 6. In an ideal world I'd like a private room but it's not a priority for me and I'm not paying extra for it.
My father on the other hand 'thinks' he wants a private room but we have found that he is a lot better in a semi private because several things have happened him while in hospital in a room on his own and you could be there a fair old while if you couldn't get to the bell yourself or had no one there to call for help! So from that point of view I think there is a lot to be said for a shared room, one other patient is enough though but that's the luck of the draw probably.
Days can be long and boring in hospital so a good room mate is great for chat and diversion but a bad one is awful, my father's last trip into hospital had him sharing with someone who did not utter one word to him in the space of the week and even worse hogged the remote for the tv and seemed to think it was for his use solely which meant the news on once a day and off for the rest of the day. In the finish I had to actually complain about it and luckily there was another spare bed and my father was moved.