NO. ALT attribute must not be optional. Just put an empty alt in for decorative images and learn how to do sensible alts or long_desc for other images.

And many of the supposedly decorative images are used functionally, in which case they need proper alts.

For images that are purely decorative including an empty alt attrib is valid. People using screen readers (and people with images turned off[1]) don't need to hear (or read)"SMALL RED BULLET" for all 7 items in the list.

[1] I often have images turned off. I'm using a mobile broadband dongle. My ISP uses horrible proxies to compress images. I'm in the UK. The IP of the proxies is 1.2.3.9 through 1.2.3.12 - this is sub-optimal for many obvious reasons. Bypassing this proxy is trivial, but means I download a lot more data.

I typically use "-" or "*" as an alt for bullet images in text, and similar decorative markers. It seems to make more sense to me to emphasize that there's a list.

The only reason I'm still using them is that they don't charge for MB or GB; I pay for three months and get "unlimited surfing". They block some stuff after you hit 1GB, but that's trivially easy to get around. Which I do, since they've said I get unlimited web use.

You can't solve a social problem (content providers who don't care) with a technical limitation (required alt tags).