There is a lot of editing traffic right now on Sarah Palin’s Wikipedia article, thanks to both the unrelenting glare of the national spotlight, the relative lack of alternate sources, and the rumors that somebody from the McCain/Palin campaign was involved in whitewashing that article just before she was announced as the VP pick.
Some online sources are linking directly to the current version as a reference, though. While I’m not qualified to comment on the wisdom of citing Wikipedia as a reference in your big professional news source, I would like to suggest an alternate approach to those who do:
use a permanent link to the revision you’re citing.
Instead of copying the generic URL, look to the left of the article text for an item labeled “Permanent link”. This item will provide a link to the specific revision you’re reading, even if the article gets changed later on. Your readers can then go directly to the version you saw; if there are any newer versions, they can read those as well. (There’s also an item labeled “Cite this page”, which puts the permalink and associated details into APA, MLA, Chicago, AMA, and other citation formats for bibliographies.)
Another potential option, if you’re discussing a specific change or set of changes, would be to link the diff. This will show you the changes made in a particular revision or series of revisions. Diff links are available in the article history.
Permanent links will look like “http://en.wikipedia.org/w/index.php?title=Sarah_Palin&oldid=235045124“. Diff links will generally look like “http://en.wikipedia.org/w/index.php?title=Sarah_Palin&diff=prev&oldid=235045393“, though the specifics of the diff link will vary based on which revisions you’re comparing.
These links work because MediaWiki, Wikipedia’s software, keeps (and has always kept!) individual revisions of articles in the article history. Revisions are kept indefinitely in the article history, though (on Wikipedia at least) a rare few are removed for blatant libel, copyright violations, or disclosure of private personal information. You can see the history of any article by clicking the “history” tab above the article text or by adding ?action=history at the end of the URL; the entries there can show you who changed the article, what exactly they did, and when they did it.
Finally, I should point out that lots of other sites use MediaWiki — these tricks don’t just work on Wikipedia. You may have to look for different link names depending on the language and the local settings, though, and other wikis may have different policies on deleting revisions.