Recently, Twitter has very much gone mainstream (at least in the UK). Even for a while before that, Twitter has been becoming more than just a microblogging service. It is certainly about a lot more than the famous prompt, “What are you doing?”, suggests.

Twitter is used by different people for a wide variety of purposes now. But due to the space constraints, it requires a fair bit of creativity on the Twitter user’s part. Twitter has almost developed a language of its own.

Very quickly, a convention developed whereby @username signified that this tweet is a reply to one of that user’s recent tweets. Twitter recognised this and built the functionality into the system. Later on, #hashtag acted as a tag for your tweet, the idea being to make it easy to find tweets on certain subjects using a site like #hashtags or Twitter’s own search function. Even more recently, the retweet (now commonly signified by RT) has emerged as a popular way to share other people’s great tweets.

What does this have to do with social bookmarking? Well, a large amount of retweets are just interesting links. That means that a lot of original tweets are just interesting links. But hang on — isn’t a social bookmarking service like Delicious more suitable for sharing interesting links?

It should be, but it’s not. Now let us get one thing straight here. I am a huge fan of Delicious. I have been using it for over four years now, and in that time I have amassed a collection of 7,493 bookmarks across my three accounts. And I won’t stop using it any time soon.

But sometimes, I find it much more satisfying to just paste a URL into Twitter and share the link that way. It is pretty clear that a lot of people do too.

Take the two most recent posts on this blog: ‘Why are newspapers hiding their niche content?‘ and ‘The Edinburgh Twestival‘. Both of these posts were shared around a bit on Twitter.

Certainly, you would expect that for a post about the Edinburgh Twestival. People interested in that post are likely to be Twitter users. This post was shared by five different people (including, it has to be said, me) on Twitter. Four of them were retweets of my original tweet. Google Analytics suggests that 15 visitors landed on the page from the Twitter website (and that doesn’t include any visits that came from Twitter clients, Twitter streams embedded on webpages, etc.). No one shared it on Delicious.

As for the post about RSS feeds, it was shared by four people on Twitter (including me again), one of which was a retweet. It was also shared by four people on Delicious. But three of those people are also the three people who shared it on Twitter! Delicious doesn’t timestamp entries, but I am pretty sure all of them posted to Delicious after posting it to Twitter (let me know if I’m wrong about that). Very probably, two of them discovered it through Twitter rather than anywhere else. So far, the post has had 18 visitors from Twitter, and just five from Delicious.

So is Twitter doing the job of sharing interesting links better than Delicious, the daddy of social bookmarking sites? Almost certainly. And it struck me why while I watched the video currently sitting on the dead / dormant Ma.gnolia website. Ma.gnolia was another social bookmarking website, that was recently taken down for good by a massive database problem. The video is a post-mortem on Ma.gnolia, but it also feels a little bit like a post-mortem on social bookmarking as a whole.

During the interview, Larry Halff points out that the biggest link-sharing website is not Delicious as is commonly suggested — it’s Facebook. It reminds me of the often-forgotten fact that the biggest photo-sharing website is not Flickr, nor is it even Imageshack or Photobucket — it’s Facebook.

This is not because Facebook is better than Flickr for sharing your photos — far from it. Nor is it remotely as good as Delicious for link-sharing. But Facebook is certainly the best place for sharing your photos and link-sharing. That is for one simple reason: Facebook has more users, meaning that you can reach more people more quickly. It’s what Facebook like to call the social graph. It doesn’t matter if the functionality is a bit basic. What matters is that all your friends are on it.

Twitter is no Facebook. While most of my “real life” friends are on Facebook, Twitter has just a smattering of my real life friends. But I follow a great deal of people whose content I just find interesting — bloggers and other online associates with whom I have built a digital acquaintanceship over the years.

Most importantly when it comes to reaching a large amount of people, I know that Twitter is extremely addictive. I know that dozens of my Twitter followers will have a Twitter application of some kind open. I am watching the messages from them tumble down the screen all the time. It feels like I’m having a conversation. I know that I will reach a lot of people by posting a link in Twitter. Then I could have a conversation with people who are interested in that link.

That sense of vibrancy just isn’t there in Delicious. The reason? This social bookmarking service just isn’t social enough. Its social functionality basically extends to being able to add other users to your ‘network’, and being able to inform them of links you think they will find interesting by using a special tag. And that’s it. There are no comments. There is no conversation. There is near enough no social. Just lists of links.

Is there the scope for a TweetDeck-style Delicious application? You could leave it open all day and watch the links from your friends stream in, just as we watch our friends’ tweets. You could use the notes section to leave comments (have a conversation). There could be special tags that allow you to use the notes section to reply to your friends.

I have seen people tag their bookmarks as via:username to signify how they found the link — but Delicious doesn’t appear to recognise it in any special way. Twitter were really smart to capitalise on the @replies convention, because it has made Twitter much more of a social tool. Delicious feels stagnant in comparison. But it seems like it could be easy to fix. So why don’t they?