Web 2.5 will be about creating safe, supportive, and effective places for structured collaboration to take place:
"Safe" will mean not only that information contributors are protected by mechanisms that insure that "only people who should see x, see x", but also that there are mechanisms to appropriately build trust in those contributors among consumers of the information. Seller ratings on eBay are the poster child for what's meant here. A prediction -- we're bound to see, at some point, a "portable online credibility profile service" that is analogous to a financial credit rating. People with an interest in being perceived to be credible online will register their personas on different sites with a third-party service, credibility ratings of these personas will be aggregated (scraped or parsed at minimum if APIs or RSS extension feeds aren't there for this), and as liquidity builds in such a service, sites will incorporate this into their platforms (as Truste vouches for the security of a site, these services will vouch for the reputations of participants in a site). At an even more technical level, platforms must and will evolve to support complex "subsite" structures with sophisticated permissioning schemes. .LRN provides a good example of an advanced architecture for this.
"Supportive" will mean that both contribution and consumption of information is coached and encouraged. Assuming "safe", many more people could be using blogs to share information to their own and their colleagues' and friends' benefit, but they may feel awkward or unsure about Why/ what/ how. Well designed applications will provide not just "defense-in-depth" help mechanisms for when people have problems, but more extensive tours and ongoing coaching for users as they progress from new to more experienced in their familiarity with the system. For example, earlier incarnations of the ArsDigita Community System featured a "Curriculum System" module to help people track what they've already learned and what they still need to know to use a system effectively (See http://philip.greenspun.com/doc/curriculum.html).
"Effective" will mean that the contribution and consumption of information in applications is made both simple and obvious. Applications like our restaurant review experiment are especially useful because the information is easy to contribute (the provided structure prompts, but is flexible enough to accomodate orthogonal descriptions) and consume (the data can be viewed geospatially on the map, or via different sort options).
