Last night GoogleGuy stopped by to make a statement in the Google's 302 Redirect Problem thread at WebmasterWorld. In that thread GoogleGuy said in msg #:108:
We've been steadily improving our heuristics for 302s based on the feedback that you've sent us. There have been two recent changes that I know of. We changed things so that site: won't return results from other sites in the supplemental results. We are also changing some of the core heuristics for the results for 302s. I believe that most of these changes are out, but there may be a few more in the pipeline.
Note that for inurl: and allinurl: searches, results from other sites are perfectly valid. So if you own yoursite.com and do a search allinurl:www.yoursite.com, it's a completely valid result to get a url from www.someothersite.com/resources?url=www.yoursite.com, for example. That's how inurl: and allinurl: are supposed to work--they match all docs with the requested terms in the url, not just docs on www.yoursite.com. That doesn't imply any problem/hijacking/issue; just that someone else had your domain name in their url.
Thank you for the feedback that people have given us about 302s. I'd be interested to hear if anyone sees a result where site:yoursite.com returns urls from domains other than yoursite.com. You might want to wait another few days before checking though, to give things time to get fully out. I have to duck out right now, but I'll try to stop by and give more details as things are more fully deployed.
He goes on to explain that this has already been applied to the Google results. In addition, they might be adding methods for you to still locate hijack attempts with a filter=0 command.