It feels like there's two possible explanations here. One is that somehow the website has been incorrectly flagged or blacklisted, like the example he mentions with Bing. In that case, it seems like it'd be at least nice for Google to be able to look into it, but it also might be the sort of thing where Google just decides it's not worth the effort. The other possibility is that Google just updated their search algor…
The problem is that there are very few viable distribution channels that we are forced to rely on companies like Google. What other viable choices does this site have aside from Google?
The only question is whether this site is one of these or not - and even if it's not, a certain number of 'false positives' is acceptable and less strict filters definitely are not. If you're running a site that's skirting the line between spam and not-spam, then either you take on the risk that you might be dropped by google and others, or (perhaps preferably) stop doing that thing and do something substantially different.