Joel Spolsky - Strategy Letter VI:

"The third phase with PCs was Macintosh and Windows. A standard, consistent user interface with features like multiple windows and the Clipboard designed so that applications could work together. The increased usability and power we got out of the new GUIs made personal computing explode.

So if history repeats itself, we can expect some standardization of Ajax user interfaces to happen in the same way we got Microsoft Windows. Somebody is going to write a compelling SDK that you can use to make powerful Ajax applications with common user interface elements that work together."