APIs and feeds.
With the increase of sites providing APIs RSS feeds etc to include information into your own site I see the way that web sites are created and implemented changing.
Take for example a new company who wants to sell its product on the web.
One way would be to build a site from scratch implementing functions to upload images create a set of images for each product. And display them along with the description of the product.
What could be done is the new company creates an account on an image site like flickr uploads the images to there and create the sets also within the flickr site. The feed for the image set could then be implemented into the companies’ site to provide the images on the product description page.
Following on from this the company could also create a feed for this product including the images description etc to allow sellers to be able to use this feed in there site to provide the information on the product. This would allow any changes to the product description to filter down to all sellers implementing the feed.
I see these services as data sources rather like the databases that drive dynamic sites. Implementing the data the same as you would with any other data source. Sites would become mashups of data ported into the one place. Maintaining all these data sources could become a nightmare editing images sets on one site the description on another product support forums on another. But this too could be simplified by implementing another set of APIs or importing and using gadgets, thus allowing the maintenance to be centralised and simplified.