When is the social curation bubble going to burst?

You just can’t move for social curation services right now. The biggest noise might be coming from Pinterest, which is growing like a weed — but whether it’s the new-look Delicious, Switzerland’s Paperli, shopping curation site Svpply, image service Mlkshk or another site, the fact is that almost everybody seems to want to help you save and sort and share the things you find on the web right now.

With this swirl of activity, then, it’s no surprise to hear that Parisian service Pearltrees — slogan “collect, organize, discover” — has just raised another $6 million of funding, led by local conglomerate Groupe Accueil.

The company, which has been running in public since 2009, welcomed the injection of funds as a way to help expand and scale up its system for bookmarking and organizing, which is based around a clustered visual interface.

And it needs that scale. Right now Pearltrees is small and has moderate momentum, building up 350,000 users in the past three years. Pinterest, by comparison, has achieved around registered 10 million in the same sort of time — and one study suggests it is now one of the web’s biggest drivers of traffic.

When I made the comparison between the two services, however, Pearltrees’ marketing chief François Rocaboy objected.

“The two services are really different,” he said, reasoning that Pearltrees bookmarks web pages, is used for organization and operates a Freemium model.

And it’s true, those are all things that Pinterest doesn’t get used for much of these things today. But the reality is that not every company in this space can succeed because they are all competing for the same sorts of attention patterns.

Just before Christmas I wrote about the Italian recommendation service Circleme, and wondered whether it could convince people to keep all of their interests and passions listed in one place. Social curation exists in a complex space for organization and discovery that overlaps with everything from to-do lists to tagging, from bookmarking to recommendations… and, of course, big sharing platforms like Facebook, Twitter and Tumblr. To say it’s a competitive area is an understatement.

But there’s an extra difficulty, too, for this new breed of social curation services. Getting something out of them requires some significant effort from users, because they have to explicitly engage with the product to get the most out of it. For the most part, the quality of information you can get out of a service like Pearltrees is directly correlated to the amount of effort you put in — a spin on the idea of participation inequality better known as “1 percent rule”.

Creation is very difficult. Curation is hard. Consumption, on the other hand, is relatively easy. That’s why a site like Tumblr can go crazy, because it balances each element of that pyramid perfectly.

And it’s why I can’t help feeling that there is a bubble here, as everyone speculates on an idea in the hope of backing a big winner. The balance just feels out of kilter.

It’s understandable, of course, that this is an enticing market. The tools available now are extremely powerful, and they connect to vast amounts of data that pour out of the Web. Combine that with the fact that the social layer is now pretty mature, and there’s very good reason why the next level of ideas are all about how to make the information better.

But is there really enough appetite to satisfy the supply? Is the one percent enough? Is the ten percent? Are there enough neat freaks and hyper-organized users in the world to support all of these businesses?

Pinterest has reached the scale of millions partly because it understands the attention pyramid — but I’m not sure everyone fighting it out in this arena does.