Why do some online communities succeed, like Second Life, Facebook and, well, this one, and some fail?

The answer may be in what their communities think about 'giving' and it can tell us a lot about people in general.

Everyone does something on social sites for a reason. People like to 'get paid' even if that doesn't mean money. It is why people submit articles to Digg - submitters get the satisfaction of knowing they brought an interesting article to people that they may not have found themselves. Or, in the case of Newsvine, they may literally be getting paid to write interesting articles for the community.

Jörgen Skågeby of Linköping University in Sweden has broken this into five aspects of "giving" and it can tell us a lot about who we are as a society on a macro-level and on a micro-level, like here. Those five aspects are:

Initiative - Advice to a stranger, a useful URL, making a file available.

Direction - A public gift, like an MP3 from a band to a group of listeners, a photographer sharing their work on ImageShack.

Incentive - If you give, you get. BitTorrent and file sharing service that offer you things you want in return for sharing it with others.

Identification - an anonymous gift is an entirely different mindset than a public one. Myspace as opposed to anonymous file sharing.

Limitation - a trial version of software, for example, is different than freeware.

These only talking giving and not about getting. What people 'get' in return is implied. A trial version of software might lead to a full purchase, one MP3 may lead to a listener buying a CD, some BitTorrent users like tweaking large media companies so they want to share files. Everyone is 'getting paid' in that sense.

What about science and science sites? Some scientists like to write but why would that be the case? Writing peer reviewed articles is almost as thankless as doing the peer reviewing. On a site such as this one, most writers will not make enough in advertising revenue to change their lifestyles. So there must be other reasons.

Those other reasons are how empires are made in the social community world. I don't truly understand a site like Dogster.com, which seems to be Friendster - for dogs - but it doubled its users last year and made over a million dollars. That is an unqualified success.

The dogs, the focus of the site, aren't really getting anything out of it but the people are. So it may be with science blogging. Nothing in science itself is materially changed because we write about it. Stars are not born, biology is not advanced, the mysteries of the brain are not solved. Yet we started this as a private beta with just a few writers in the beginning of February and had 100,000 readers in just the last week.

Why did that happen? Science is inevitably intertwined with science policy. By writing about science, and having people read about science, we affect policy and voting so if science is important to us we 'get paid' by knowing we have made a difference. Our gift is good science and at that we succeed but can you really even be a failure if your costs are low? Not on a balance sheet, but a failure in this kind of site would be if scientists don't know their writing - their gifts to society - are appreciated and so they stop doing it. Everyone knows how many readers they get for an article but a pat on the back from other writers or a healthy discourse with readers in the comments section is a good thing also.

So if you're reading this, 'gift' something back to the community. Sign up as a registered member, vote for articles you like on the site ( that little + you see below "Peers" ), leave a comment, refer your friends, submit an article here to a large social site. Or even write your own articles if you know science and want to write about it.

That's the Initiative gift Skågeby talks about above. Writers feel good knowing you're reading and they'll feel good if they know you care.

'Gifting' is not a sometimes thing, it really is a central human activity. As our reach extends to more and more online social and science communities, how we 'gift' will really shape who we are.