I do believe the problem is with the following paragraph:
Attribution — You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work).
(emphasis is mine)
What's this manner specified? I think this is too subjective. How can you just point at people and say they are ilegal using your content if you didn't specified what exactly this "attribution" means?
The only complete reference about this subject that I found is within an official blog postofficial blog post (it even has the website you're concerned about as an example).
I do believe it would made no harm a simple url below the cc-wiki image in SO footer, named "Attribution Guidelines" that are contained in this postthis post. Doing this way people have no excuse of "misunderstanding" attribution guidelines since you explicity said what you need to to when using SO content.