We haven't covered the proxy hijacks issue in a while, but a new WebmasterWorld thread has brought it back to life. The individual said his web site suffered a hijack in Google:
Iv just notice that a russian website has Proxy Hijacked our website and got it indexed in G results.. We have noticed a steady decline in our SERP positions since end of Jan. I found the copy site by doing a "quote" search of the tittle in G.
WebmasterWorld administrator, Tedster, links to the old 2007 thread on the topic and quotes the part on how to defend yourself from such issues.
How you stop this problem is to use REVERSE and FORWARD DNS to validate that Googlebot is coming from an actual Google IP, which returns a domain name that contains ".googlebot.com". If the reverse DNS of the IP that claims to be Googlebot doesn't contain ".googlebot.com", you simply bounce them.
Forum discussion at WebmasterWorld.