Apigee
Apigee is a new service from Sonoa systems that acts as proxy for API's. That provides:
Analytics and Protection for APIs and Mashups
It does this by creating a proxy that all your requests go through and doing work on those proxies. This is a really interesting idea since API's are the one area of technology that are essentially unmeasured. All other forms of web traffic are easily measured, but rarely API's.
But I'd hate to use a proxy simply because: when the proxy goes down, your API goes down. Everything goes down. There's of course added latency, security is not a huge concern, but SSL isn't an option. Unless of course the proxy get's taken over.
Ideally if I could install that proxy locally, I'd remove this problem - and perhaps this is Apigee's monetization plan. For example, I've pretty much assumed that in Arecibo, our servers can go down and that this will not leave your site in-operable.