Sharing

So... I've been writing relatively compulsively in this blog. I'm talking a lot with my family. What's up with this human "need to share"??
On the one hand, I see that it's a facilitator for social bonds and community, which probably leads to higher survival rates. So we've got the Darwin bit going on. Second, it seems to be a cultural thing. Some peoples are 'all up in the bizness' of their family and friends, some aren't. And finally some of us individuals keep to ourselves, while others definitely share everything... (you know them: "random medical info on the bus" person, "tells life history when confined in small spaces with others" guy [often found on long flights and train rides, or in broken elevators], and my perennial favorite "running commentary on everything around them" folks)
Now, I'm not quite to the point where I'm reading roadsigns aloud, but I AM to the point where that behavior seems more understandable than it ever has before. There's something about sharing an experience that makes everything about it more vivid, rich, and exciting. Why is it that dining alone is so much less satisfying... do we need other people to validate not just our opinions, but the experience itself?