The origins of wildcache are fairly simple. It started as WPCP (the WordPress caching proxy.) We at Automattic, found ourselves in need of a caching solution capable of serving millions of feeds quickly, and efficiently. I built this piece of software to be a man-in-the-middle reverse caching proxy (or content accelerator.) The project was quite successful, and the software was able to serve tens of millions of hits per day from a single web server for several months. Load on the web server was generally very low, and load across the backend web servers dropped by 10% to 15% . Another member at Automattic was developing a different caching system which was much more distributed and efficient (and also much much more intertwined on a fundamental level with the quirks of wordpress.com.) WPCP was no longer needed, and removed from the repository. I asked that I be allowed to open source the software feeling that, while Automattic was lucky to be at a point where such a project could be undertaken, many not so advanced projects still have a genuine need for the void that we filled. Wildcache is born.
Wildcache is a lightweight php based (yes that means it runs on top of a web server) reverse-proxy/content accelerator. My feeling is that there is little choice for startups and lightweight webmasters who may be suffering the burdens of success. Many new businesses find themselves struggling with the growth of their web services (and the load put apon the servers running those services) versus the inability to justify the purchase of expensive hardware (or software) content acceleration solutions.
Wildcache takes the stance that permanence is more important than freshness. Once an item is cached it remains cached until it expires (via a hard coded variable) or until you explicitly invalidate the url. One thing that Wildcache does give you which is difficult to find in cheap solutions is the ability to invalidate cached objects via regular expression matches. This makes Wildcache very easy to work with.
Furthermore, bring written in php, and in a very extend-able manner, it should be easy enough for anyone capable of building a web service to make Wildcache suite their needs. I always envisioned Wildcache working with you, instead of forcing you to adhere to its principles of how a web service should work.