People in groups of more than two or so. Even two can be too many!
Being in a relationship.
I disagree. I love being married to my wife. We don't spend every minute together, but I know she's there and I'm there for her if needed. And when we are together, it's very good.
Sex.
Did you see that Ted talk someone posted this morning? As it turns out (according to the speaker), sex is critical for adults.
@celticagent I looked for the article to which you refer and came up empty. Can you provide a link?