Separate vendor specific forums look like a good idea at first glance, but sooner or later, the vendors will "phase out".
In a year or so, we might already have a couple dozen hardware vendors, some with their own chips, others just sticking together components.
Also, a lot of the vendors won't be in business for too long, so eventually, you'll end up with forums for hardware vendors that no longer exist.
Also, some vendors may still exists but not have a new product for a long time. At the same time, they'll be in "planning phase" for a new product for some years before you can really tell that they're no longer on the market.
It could become a real hassle to find out which vendor forum should remain open and which one should be archived.
But, I think I have a solution:
Sell vendor specific forums!
For a fee of a handfull BTC per month, let the vendors have their own subforum within "Mining Hardware".
Give them some moderator privileges, like stickiying their own advertisement threads, but obviously, don't let them delete posts or threads.
Once they no longer pay their monthly rent, take moderator privileges from them, and leave the forum for a couple months, for users' complaints.
Okay, seriously, that's probably not a such bad idea, but do we really want this?