In a world where more and more people want to receive their email on PDAs, pagers, and cell phones, there is less and less place for the bloat of HTML email.
If you're message can't be conveyed in simple plain-text that can be displayed on whatever device I use to check my email, then make a webpage, post it somewhere, and email me the URL. I'll know what to expect, then, and can choose to launch my browser and visit at MY convenience.