"Google's problem" = "Search engine optimization" = people with an agenda trying to game the algorithm (so their site gets ranked higher than better ones). For example, linkspam makes "number of inbound links" a less reliable metric of site quality than it would otherwise be.

If something is known to be used as a proxy for quality and people are rewarded accordingly, then you'll end up with people trying to achieve the proxy for quality at the expense of actual quality.

I'm not sure what that has to do with the original topic, though. Are you anticipating that quacks will go on sites like this and say "You should buy my snake oil - look at all these sockpuppets that it's helped!"