A Web API lets you use a web site’s computers, data, algorithms, and functions to create your own web services. Google, Ebay, Amazon, Yahoo, and many other web services have APIs.
RSS is like an API for content. RSS gives you access to a web site’s data just like an API gives you access to a web site’s computing power. Most important, RSS gives you access to your data that you have locked up on a web site.
Every Web 1.0 company will have to decide what content they will open with RSS. For example, Amazon already makes their content like their book catalog available through their API. But will Amazon open up user-contributed content through RSS?
Someone once said, they dont visit sites which dont have RSS. I laughed then, but now I dont. I wouldnt dare join a service or site which doesnt support good clean RSS/ATOM output. Its important to get my data out on my own terms, but I would also like to get my attention data out. This is the next step but RSS will have a role to play in this too. I remember listening to a podcast (cant remember which one) where they spoke about how the public will be expecting tools and services like they experience online. Its happening, I've noticed a large amount of discussion about gmail vs thunderbird just recently. Why is search online better than search on the desktop or on your companys intranet?
Blogdigger has a good entry explaining why there using RSS through-out there system.