bird - 11:33 am on Dec 8, 2010 (gmt 0)
Amazon's use of the content is licensed under Creative Commons, the alternative to traditional copyright that Wikipedia uses for all of its user-sourced encyclopedia content.
A Creative Commons license is not an "alternative" to traditional copyright, it's a straightforward application thereof. Amazon should have asked a lawyer who actually knows what he's talking about before writing this.
Other than that, Amazon uses those data exactly for their intended purpose, as do probably thousands of other sites out there. They also don't need to "scrape" Wikipedia, they certainly use the official RDF data dump (both for the initial download and hopefully regular updates). This may indeed lessen Wikipedia's server load as Fribble notes.
Also, Wikipedia has no interest at all in "ranking" on Google. Their own site is primarily intended to be used by editors, with other sites using the resulting content for display to the general public. Indeed, the fact that Wikipedia pages *do* rank well for many keywords costs them a lot of money for bandwidth, which they'd really prefer to spend for more productive purposes.
In summary: What Amazon does here is good for Wikipedia in pretty much every aspect. People getting annoyed about it apparently haven't quite grasped yet why the project exists in the first place.