Seems like there's a bit of a bug when using 'Save for web and devices' with thin weights of type in CS5 for Mac. Although thin type looks fine while working in Illustrator, as soon as you enter the 'Save for web' dialogue, it gets badly mangled. Looks like this issue has been present at least since CS4. It does not happen in Photoshop. It looks particularly bad for light text on a dark background.
Some people may say "sure, Illustrator is not really meant for intensive bitmap work". However, with features like 'pixel preview' and 'snap to pixel', Illustrator has (generally) become a very viable tool for web design, and personally I much prefer it to Photoshop. It is also clear that Adobe intends it to be usable in this manner. So the anti-aliasing render bug is definitely a problem. Just surprised they didn't address it when CS5 was born.
I put up some example images on http://www.thesheep.co.uk/2011/06/24/illustrator-save-for-web-anti-ali asing-problems/ to illustrate the problem.
Does anyone have any clever work-arounds for this? It's a bit annoying to have to move stuff over to PS before exporting, but maybe that's what I have to do. Hopefully Adobe will address this soon.
