One of the things that I really appreciate about Stack Overflow is that it dislodged the perpetually low-quality but pervasive Experts Exchange from the top spots in search results. I'm consistently amazed at how quickly relevant, informative answers are provided.
That being said, there's a worrying trend where clone sites like "efreedom" are moving up in the search results simply by capitalizing on the large corpus of data generously provided by Stack Overflow.
While I appreciate a licensing model that allows people to share the content contributed by so many users, this will be subject to rampant abuse and without some kind of mechanism to restrict the activity of these clone sites I worry that Stack Overflow's success will be its failure, drowning in a sea of identical results, just one site of many with exactly the same information.
We have the ability here to down-vote, close, or delete questions that are inappropriate or somehow damaging to the community. Google provides no similar method for demoting parasitic sites.
Wikipedia suffers from the same sort of problem, but as their subject material is extremely focused and highly optimized for searching by the manner in which it is defined, it is not as significant an issue. Searching for information on a subject by name is an entirely different process than trying to resolve a tricky technical problem or track down how to overcome a particular error where there is no standard approach to be taken.
Is there anything that can be done from a licensing perspective that prevents the whole-sale duplication of answers without infringing on the reasonable rights of people to make use of the data for more constructive purposes?