UPDATE: As Danny pointed out in this thread, what's happened to Matt Cutts' blog is not really "hijacking", though it does bear similarities. What has happened, is that the source of a story, in this case, Matt's blog, has been washed out of the results pages by duplicates on other sites - it's part of a noticeable problem in the way that Search engines hanndle duplicate content, and the trouble they have determining the original. In particular, Google seem very prone to this - and as you can read below, no one is exempt...
Well, strictly speaking it may not actually be what we've come to think of as the classic Google 302 Hijack, where one site can take over the rank of anothers by 302'ing for Google only to the victim site, but DarkSEOTeam are certainly having some fun with him.
Dayo UK discovered this in a thread about Google's dupe content filters, and member reseller sums up what is most likely going on:
What you are seeng my UK friend, is stealing contents in day light and Google isn´t able, as usual, to differentiate between the original contents and the duplicates. And as many fellow members, which sites either dropped totally from the index or just lost much of their rankings because of the same problem, have reported on this thread. It is a real disaster that both Google and the webmasters community are phasing.
We've talked about this before, and i understood that new filters in place were doing a better job, but when an employee of Google's site can be "hijacked" in this way, because Google cannot distinguish between original and stolen/copied content, it does rather hightlight the problem doesn't it?