Social networks: Perhaps the most obviously social of all social software are those that enable the creation of personal networks of friends and other like-minded people. The use of services like MySpace 40 and Facebook 41 has become almost ubiquitous among young people in many countries. The average age of users is now starting to grow as they break away from their core teenage and college student markets.42 Meanwhile, LinkedIn 43 has become a favourite networking tool among business people. Once again, medics and scientists are following the mainstream with sites like Sermo 44 for clinicians and Nature Network for scientists.45 These environments are not only for finding and contacting new people with shared interests (though they are good for that too and therefore have potential in everything from job-seeking to dating), they also enable the creation of discussion groups and allow users to efficiently follow the activities (e.g., in terms of posts and comments) of others whose views they find interesting. Correctly implemented and used, these services therefore have great potential to make scientific discourse more immediate, efficient and open. A major unanswered question, however, is the interoperability and openness of the services themselves. No one wants to have to register separately on multiple different sites or lock up their details in a system over which they have no control. Federated authentication technologies like OpenID 46 and other approaches to interoperability hold promise, but it remains to be seen how enthusiastically they will be embraced by the operators of social networking services, and how receptive they will be to the idea of partial cooperation rather than outright competition.
Classified advertising: This may seem like a strange category to include here, but newspaper small ads are arguably the original grassroots participative publishing service. It is perhaps no coincidence, then, that they have been among the first areas of traditional publishing to fall victim to lean and radical Web 2.0 startups, most famously craigslist.47 Particularly among careers services, there is also keen competition to turn simple ads services into social networks, as epitomized by Jobster,48 and the distinction between social networks and career services is only likely to blur further. Though some very large employers, notably Britain's National Health Service 49 have established their own online jobs boards, effectively disintermediating their former advertising outlets, this revolution has yet to hit the medical and scientific advertising realm with full force. One early sign of the changes to come was the switch by NatureJobs in late 2006 from an arrangement in which online ads were sold as part of a portfolio of products to a 'freemium' model 50 in which simple online listings are provided free and other services such as rich, targeted or print advertisements are sold as add-ons. This reflects the different economics of operating online, where the marginal cost to serve an extra advertiser is low and the benefits of providing a single comprehensive jobs database high.
Markets: EBay 51 is in some ways the definitive Web 2.0 company: it is a pure market in which the company itself does not own any of the goods being traded. Similarly, other services, such as Elance 52 specialize in matching skilled workers to employees with projects that they wish to outsource. In the scientific space, the online trading of physical goods (such as used laboratory equipment) is not yet commonplace, though it might become so in the future. In contrast, the matching of highly trained people to problems does have some traction in the form of 'knowledge markets' such as InnoCentive.53 These are still at an early stage, and they are mostly used by commercial organisations such as pharmaceutical companies, but it is not hard to imagine academic research groups doing the same one day if (as it should) this approach enables them to achieve their goals more quickly and at lower cost.
