into types of motherboards people care about:
SLI
dual processor socket
microATX/HTPC

and put CPU/chipset into a separate topic

Most people have absolutely no clue what any of those terms mean and would only get confused. Not to mention that there are no radical differences between motherboards from any of these classes. It's all the same PC stuff.

Also, you forgot the most common standard ATX motherboards

LOL. I guess it depends who you're targetting the forums towards...the average user or the techie :-)

Techies don't use regular ATX motherboards any more...it's all about: SLI, overclocking, HTPC ;-)

Hum.. I still use computers with AT motherboards

LOL. What kind of software can you even run on a computer w/ a slow AT motherboard? :-)

LOL You'd be surprised. AT doesn't necessarily mean THAT ancient. Some of the earlier, best AMD chips are still running on a couple of mine...using Windows ME. Yeah, I know....a lame O/S (before Nodsu hits me) but functional nonetheless.

What do you think peole did with computers in the 20th century?

That's right, they did exactly the same things as today, only they had less bloated software and more clever users

Aren't ATX mobos pretty much the most common in current use?

The mainboards are catagorised by form factor (AT, ATX, BTX, etc) and further catagorised by socket type. That's just the way it is and TS is just arranging them by the recognised way of doing things.

That said, If TS wanted to maintain a database of all motherboards under the sun, searchable by various criteria as listed by yourself (and combinations thereof), it would be pretty useful - but who's going to do the work for it and keep it up to date? - no small task.

Technically speaking - the first thing I want to know about a potential new mobo is what kind of case it belongs to compared to what kind of case I have/want.

I've had win XP running on old pentium 3's and 64Mb of ram in mobo's making the transition from AT to ATX, and while a little sluggish, they've been perfectly useable for their intended purposes.

It's all about perspective I guess.

well i think maybe organize them by the chipsets due to that most boards are relatively the same from chip to chip. so have VIA, NF2, NF3, NF4, Crossfire, and so on. that is how it is at DFI-Street and it seems to be a nice way to do it, cause you can find the probs that peeps have with the same chipset as your own.