Yes, it’s a really interesting problem. I utterly the support the right to comment and critique. I’m a big fair-use advocate, as I think corporations have used legal asymmetry to reduce the ability to defend fair use. But what Genius is doing (and the W3C annotation standard appears poised to do in a more severe way) is remove all control in all circumstances from someone being able to control any aspect of their web pages’ presentation.
In a social-good setting, I can see how CNN shouldn’t be able to post news and then be immune to even 100% reproduction in a way that’s required to provide strong critique. Courts have found in favor of that.
But in most cases, citation is the bigger factor: Long quotes or even screen captures are more defensible, useful, and transformative than “here’s a proxy-retrieved Web page that we’ve splattered lightly moderated comments all over.”