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Another thing to tell your friend. If 301s did not work, the whole web would implode. This would suck for website owners as they would never be able to change anything with a URL without losing traffic. It would suck for Google as they would have perfectly good pages that move drop out of the index for no other reason that it moved, This would mess up their search results as good quality pages would drop out of the index and this would suck for users as they would not be able to find good quality pages in Google. Google does not want to upset users as they need to users to keep using Google. If website owners were penalized in this way, they could get frustrated and stop producing good content. It is kind of a "chicken or the egg" type of explanation, but I think you get the point. All of that said, there can be issues with how 301s are used, 301s can be used incorrectly, this can mess up rankings, and that is true. But done right, 301s work, and they have to so that everyone (users, webmasters, Google) can benefit from a better web.