While reviewing, I saw a lot of tag wiki edit suggestions. I did some checks and most of them are 100% literally copied from other sites.
Most are in the first few google entries.
But unfortunately most got two approve votes later on.
For tag wiki and excerpts it is quite simple to google for the tag to find if it is a literally copied piece of text. But maybe we need a google it button from within the review page, or even an automated duplication detection?