While pursuing this endeavor, I stumbled upon a YUI article indicating that Yahoo is now providing free hosting of the minified files. Instead of downloading the files, copying them to your own Web server, and hosting them from your own site, you can now just reference the files directly from the Yahoo network. This means you get to take advantage of the enormous investment that Yahoo makes in optimizing download times (geeky stuff like edge computing, gzip compression, expires headers, etc.) - all for free. Nice.
I've gone a similar route with all of the images that I use in the FamZoo pages. I upload them to Photobucket and let those guys worry about serving them up quickly. As of today, they claim to serve up 2.7 billion images - I figure they have much more of a vested interest in making sure those images are served up quickly and reliably than I do! Again, all for free. Nice.
I love this growing trend of large Internet providers allowing others to freely leverage their massive infrastructures. This makes it all the easier for us small fry sites to provide state-of-the-art capability and service levels at very low cost.
Note for other developers using YUI and considering this move: Yahoo keeps separate directories for each version (the version number is baked into the filepath), and they indicate on their Blog that thier "current policy is to support permanent availability of legacy YUI files". So, looks like you needn't worry about your external dependencies changing or being yanked out from under you. I also suspect Yahoo will be around for a while...