I'm not sure that it's as relevant to Wikipedia as Rootology thinks it is: the decision explicitly disclaims the publisher's responsibility to remove all libel from the archives--one could merely issue a correction when the libel has been pointed out:
QUOTE
It is also noteworthy that the Court of Appeal did not suggest that potentially defamatory articles should be removed from archives altogether. In the circumstances, the Court, like the Court of Appeal, does not consider that the requirement to publish an appropriate qualification to an article contained in an Internet archive, where it has been brought to the notice of a newspaper that a libel action has been initiated in respect of that same article published in the written press, constitutes a disproportionate interference with the right to freedom of expression.
One might only be liable if one is on notice of the libel (I find it surprising that the paper didn't simply remove the article from their archive, actually--their free speech argument strikes me as absurd). Still, it's worth pondering whether this would apply to individuals who do not take actions to remove the material once they are aware of it.
It also suggests that merely reverting libel is not adequate--every time someone accesses the previous version, it's an archive view "publication." Does anyone want to guess how many libelous statements are in article contribution histories?