What they did doesn't seem "extremely minor" to me. It's about as textbook as you can get as an example of something that will piss off google. Reminds me of all the grey/black methods "facebook apps" (remember them?) would use to trick people into spamming their friends with invites. In my experience, this stuff can work in the short-run of maybe two or three years... and maybe that's all that a lot of startups really care about... flipping a company in a couple years. But if you want to build a lasting business (not sure that's the goal of RapGenius), you build a service that provides real value to people that they gladly talk about to their friends. And you approach SEO by providing interesting, fresh, rich, easily-indexable, accessible content. Not by seeding thousands of Bieber links back to your site.

In my experience the people who do these grey/black things just can't seem to flip that switch to producing value... they look for the angle, how they can parse the terms to their advantage and claim ignorance, and they cannot get out of "lawyer-think." You'll have a hard time convincing them they did anything wrong.

As for calling out their competitors, I actually don't have a problem with that. They're going to be under a microscope from now on and will otherwise be at a disadvantage. Their only reasonable course is to try to level the playing field.

Anyway, forgive the rant. I find these types of tactics gross and I'm glad they're getting penalized.