Moderate nothing. Let the ignore button do it's job.
Make a new sub-forum for each of the major manufacturers and 1 more for any new entrants to the bitcoin mining marketspace. They can be promoted to their own new sub-forum if they make it bigger and appear not to be a scam.
+1.
The vast majority of really angry posts I see are directed at one company in particular and are totally justifiable IMO. Forum administration has continued to accept advertising revenue from this particular company despite the painfully obvious fraud being committed. Simply stifling the understandably angry dissenters is akin to engaging in the fraud yourselves. I'd urge bitcointalk.org admins to either continue to maintain a very light handed approach to post moderation, but if you insist on stifling free speech, then, at the very least discontinue accepting ad revenue from companies that are plainly engaging in fraudulent activities.