I just need to import, and update this still annoyingly-popular article:
http://shoobe01.blogspot.com/2007/07/why-dont-we-use-italics-online-anyway.html
Updates will be for devices over around 250 ppi, the resolution is now getting to the point you CAN begin to emulate halftone print, so use serifs, stress and italics (or obliques) over a certain size. I'll get into this... sometime.'
Also, will need to talk a bit (here, somewhere else?) about how pixels are not halftone dots. 250 ppi is no 250 lpi... and what the difference means.