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It seems like the logic has changed or the command is being fixed. I noticed that related:www.google.com shows results, but was hard pressed to find other websites that showed any results.
As of late, this command seemed to report non-sense results anyway, maybe a fix is on the way.
I expect that the relational update is part of the larger battle against link spam. If they can devalue unrelated links they can weed out some of the spammers. I wonder how they're viewing relationship, though. Some ideas aren't in the same industry, but still have good reason to link to each other.
I posted about the related command back in March:
To me it seemed "broken," but I suspect the problem might have run deeper than this simple command and might somehow be related to BigDaddy.