This looks very interesting! I have actually been playing around with a Semantic MediaWiki instance to achieve a similar goal. The beauty of that is that you don't need to worry about a database schema ahead of time, you can just add fields as they come up. It can be queried like any other database, so if for instance you want a list of VGA cards that work in an 8-bit ISA slot then you can do that, or if you want a list of motherboards with a 32-pin EEPROM socket to use for putting XTIDE into a new flash chip then that's easy too.
The problem I have with a non-wiki format is that if someone else comes up with a new piece of data that could be added, it's not easy to include it. I am new to Semantic MediaWiki but I like the fact that anyone can do the equivalent of adding new columns to the database tables.
Regardless of the underlying implementation, I think what would make this sort of idea generally most useful is the querying. It's all well and good to record this information but what if you have a card you can't identify? Can you produce TH99 style diagrams of everything in the database, but restrict it to 8-bit ISA slots with a single VGA connector, and a PCB-edge style feature connector? Or can you have a "my hardware" section where you can add all the items you own, and then do things like ask "which network cards do I have that can read 28-pin JEDEC ROM chips?" and get a list of devices *you already have* which can do just that. Asking something like "which VGA card do I have that has a max of AGP2x and also has S-Video output?" should be just as easy.
Going further, you could even in theory ask "which CPU/sound/video cards do I own that work with this motherboard?" then sort them by speed/memory size/power use, to simplify the task of building a new retro PC with a specific goal in mind.
This is something the Vogonswiki could do pretty easily (by just installing the Semantic Mediawiki extensions) however it would need a dedicated custodian to get it off the ground, and I'm not sure there's anybody doing much editing there at the moment. I don't know whether the site is at risk of disappearing without warning. It seems stable enough but what happens if people start uploading megabytes of high resolution photos for each hardware device...