Previously even a stub page like "we have no reports of scams or ripoffs for [company name] could have triggered a Suggestion if the search volume was there. So that Suggestion alone could have a "chilling effect" on the business involved.
So yes, these kinds of Instant results would have been potentially defamatory (borderline slander, I'd say, but IANAL) and IMO they should have been removed a long time ago. In fact, there was an evolving black-hat attack vector on a competitor's reputation: performing such searches in bulk, and of course, with certain stealth precautions to get around the Google safeguards.
Of even more concern to me is the shift in singular/plural balance - a lot of research on search behavior could just have been neutered.
I don't think Google is intentionally skewing the Suggestions, but the potential for bad Suggestion data to shift traffic patterns is immense. The potential for conscious and intentional manipulation is there as well - and that possibility makes me shudder.
So with Instant, there is a newly heightened power given to Suggestions. The changes in site traffic brought about by this power need to be researched in the coming weeks and understsood. I'm sure it's more than just [scam] searches and singular/plural.