Earlier today I added some DATA URIs to a blog entry I was putting together. I was in a situation in which I couldn't host the images anywhere, and they were under 250 bytes each, so I couldn't reference them via HTTP, and nor would I want all the HTTP overhead for these small images.
It had been awhile since I'd used DATA, so I tested on Firefox, Safari, then IE7. Firefox, check... Safari, check... IE7, nope!? I assumed I'd screwed something up because not supporting data: URIs made no sense at all. Sure enough, IE7 doesn't support the scheme. It's beyond me as to why. I'd put DATA into Netscape/Mozilla/Firefox long ago, so I was sad to see the lack of support in IE. What makes it particularly funny is that in lieu of rendering the image data itself, IE lays out a generic box with the text "embedded image" in it. Instead of telling me it's an embedded image, maybe just render the data instead!