Totally agreed, motivation and information accuracy are two key elements.
I would imagine the possibility, with some serious effort involved, to categorize and mark who stands behind results, such as:
• Manufacturer, trademark / brand owner
• Affiliate / advertiser
• Information provider
• Reseller / distributor
• Hobbyist / fan club
G directory categorizes information accuracy but does not indicate (rate) motivation behind the site. It is ok to create *me too* affiliate directories but they need proper indication on SERP.
Small icons or letters beside results could immediately indicate to a customer what to expect by clicking on a link.
To draw a parallel, the results would be equivalent to postings in newsgroups, moderated versus un-moderated.
The problem I see with this is that SE would go into different business model and would not be able to follow the changes. Simply, there would be too many. Site owners could easily switch motivations and if not monitored closely the results could become misleading.
To effectively track and tag changes, directory groups need to be small and closely moderated or may need more moderators per group (in a similar fashion as WW). This may be how G directory operates today. I don't know that.
To summarize, I would prefer if results would indicate owners: (manufacturer vs. affiliate vs. hobbyist). This implicates that advanced search option would be to filter “resellers only”, etc…