Data grids and the Web

There's been a lot of talk recently about web 2.0, social networks, and cloud computing. To my way of thinking, these are very much overlapping categories. One useful technology that can be used support all of these models is the concept of a "data grid": high performance, distributed and reliable caching technology. On-Demand Enterprise has a good profile of AbeBooks.com, which uses Oracle Coherence technology to support their web site.