Google Webfont Directory
code.google.com
code.google.com
This server-side logic makes it more than just a font-face repository like I initially assumed. If you feel like rolling your own and not using Google's, you can easily download font-face kits from fontsquirrel.com.
So if your website uses a font that is used by another website which the user has already visited, the browser doesn't need to download the font again. It doesn't even need to check the modification date on Googles server.
As many fonts add ~100 KB to the download size for a page, this really makes a difference.
Here's a good example of a font Google should add -- Saab, a Gurmukhi (Punjabi) font. http://guca.sourceforge.net/typography/fonts/saab/ (free, gpl'd, unicode 4.0, opentype)
This seems to be a TrueType bug in Safari that can be circumvented by using OpenType or SVG, which I discovered can be easily prepared with this excellent little tool: http://www.fontsquirrel.com/fontface/generator
I ended up opting for my own @font-face linkage with the multiple formats converted by the aforelinked, which seems to render much better across browsers.
Shouldn't be hard for Google to implement something like this, though.
My thought is that they're hoping this will encourage more text instead of images as text. That helps them index more information and collect more data on the whole web.
http://en.wikipedia.org/wiki/Core_fonts_for_the_Web
It's not some big conspiracy, it's about making the web easier to use, easier to read, and easier to design.
TypeKit helped build part of this (http://code.google.com/apis/webfonts/docs/webfont_loader.htm...), so read what you can there.
Doubleclick ads, embedded youtube videos, centrally hosted frameworks such as jQuery, embedded RSS feed aggregation, Google Charts / sparklines, Maps, custom site search with autocomplete, Google Talk client, Picasa images, Waves, iFramed Docs/Calendars...
Dammit Google, why did I have to search my history for a link to this awesome page. Sometimes, I swear people ignore intuitive things that are just too obvious.
Then again, Twitter was abuzz with everyone freaking out about DnD in html5. Guess if Google's not holding peoples' hands they might as well be useless. I also saw a tweet where someone asked if the REST API would be available for the iPhone. I facepalmed.