"Facebook says it uses pattern recognition to find and eliminate click farms and accounts that exist solely to like pages. Since March, says Facebook, it’s “notified 200,000 Pages that we’ve protected their accounts from fake likes.” I love the way they put this: “Protected,” as if the companies hadn’t paid for them." This may be more accurate than the author of this article believes. I've read elsewhere that precise…
"Protected" might be more accurate than you think initially. One of the first things that happens when blackhat SEO experts discover a "penalty" mechanism, is they will attempt to invoke it upon their competition. Google deals with this re:bad links. Once they started penalizing, it became a new tactic to suppress competition.
But like you said, Google doesn't know who paid for them, so if they penalize spam links you can use that against competitors. There's no good solution other than "Be 100% perfect at identifying and ignoring fake links."