font selection is css3.
CSS3 is not complete and only partially implemented,
no browser yet released supports all of css3 and what support there is is buggy as the standard is not complete
absolutely pointless to include something that will NOT work in 90%+ browsers, so google have on the helpscreens of their site how to make non-css3 browsers act like they know whats going on
http://code.google.com/apis/webfonts/docs/webfont_loader.html#Example
[indent]The WebFont Loader is served through the Google AJAX Libraries API.
It provides events that are fired at different stages of the loading of the fonts. You can either write code to react to those events, or use CSS styles defined by the library to automatically make styles change when fonts have finished loading[/indent]
EDIT:: would (probably) be better to access the files off the google repositoroy, than your server,
their (Google) server farm is spread all over the world and is way faster than your server. gets you the advantage of multi-sourcing the http protocol allows only two files from each domain to parallel, but can stream 2 files from three domains (=6) at the same time.
Other sites are likely to be using the same file from google, if not now, in the near fuure, the browser may find the css already in the user tif and not dl it.