Flickr, Twitter and Facebook all work because they are primarily about people. Photos, status updates, messages and comments are all secondary, they are the social glue that help make the community work. And if you doubt me then consider this – Heather Powazek Champ, the Director of Community at Flickr has reported that:

People have fallen in love on Flickr. Some have proposed over Flickr. It’s just a delightful thing for so many people, and I get to spend my days with them.

Flickr is about the social nature of photography. Strangers meet online to comment on each others’ photography, form and join groups based on common interests and share photos that document and categorize the visible world. Likewise Twitter isn’t simply a stream of the world’s consciousness, it’s a semi-overlapping stream of activity – some public, some private and some semi-public.

It seems to me that it is the semi-public, semi-overlapping aspects that make services like Flickr and Twitter work so well because they help reinforce the social. Consider the alternative: YouTube for all it’s success as a video uploading and publishing service it is a mess when it comes to its community. In fact there’s no community, there are just banal comments which often don’t get much better than “LOL”.

Flickr on the other hand doesn’t try to be an all purpose photo publishing service, it’s a photo-sharing service primarily aimed at sharing photos with your friends, family and others with a common interest. That’s not to say that there isn’t also a public sharing aspect to Flickr; indeed most of the photos on this blog (including the one used in this post) are from Flickr, and in the main, from people I don’t know. There is a public aspect to Flickr, just as there is a public aspect to Twitter, but these aren’t the primary use cases. The primary use cases are those associated with the semi-public: finding and connecting to friends; sharing photos, ideas and your thoughts with friends, that sort of thing.

The semi-public nature of these services also means that the community can, and does, develop and enforce community rules. With Flickr these are site-wide rules, as Heather Powazek Champ puts it:

“We don’t need to be the photo-sharing site for all people. We don’t need to take all comers. It’s important to me that Flickr was built on certain principles.” And so they’re defended — and evaluated — constantly.

With Twitter the rules are more personal, more contextual and as a result so are the communities. You get to choose who you follow and only those people are then part of your timeline. If you don’t follow someone then you won’t be bothered with their updates (and they can’t direct message you).

This shouldn’t be surprising since this is pretty much what happens in the real world. You have networks of friends whose conversations overlap, and whose conversations are sometimes held in private and sometimes semi-public.

So what’s all this mean? Well for one thing it means that unless you want banal comments and no real community you need to build people into your service as primary objects, rather than treating their comments, content and stuff as primary objects. You also need to work out how to allow semi-overlapping activity streams. It also probably means that you shouldn’t design for ‘user generated content’ since this will tend to make you think about the user’s content rather than the people and their community.