2) when the CSS alone is more than 10KB, reloading that on every request can make a page load slowly. If a user manages to download the style sheet at 10KB/s that's 1 second of extra load time per click on your page. At 20KB/s that's still half a second.
luna_core.css is currently sitting at 13.9KB. If you embedded that into the html, and your site got 1,000 hits per day, then that's 13.6MB per day or about 420MB per month of bandwidth usage. A more concrete example: our server does about 90,000 page requests per day; If luna_core.css was embedded in each request, then that's an extra 37.8GB per month in bandwidth usage. Small things add up.
Also remember that if your site loads slowly, visitors are probably less likely to return (well there's a lot of variables which would affect this, but this is one of them). I think the benefits of saving bandwidth and lowering load times outweighs the downside of not being able to save pages to disk (which is sort of a browser issue).
Adrian