Lately (on Server Fault at least) we've been seeing many tag wiki edits where people copy and paste content from other websites without the slightly bit of rewriting. Every site I've checked out so far has a copyright statement that disallows plagiarism, most simply require attribution, but some outright prohibit copying of their content.
It would be really helpful if a large red/white box appeared under the blue/white "What are tag wikis?" box when a paste operation is detected in the edit box. The text of the warning would be a quick reminder that copied content is usually copyrighted and the user need to check that out, and provide attribution where it's due.
I'd like to keep this as simply and unobtrusive as possible, there's plenty of people who play by the rules, and I wouldn't want them to be discouraged at all. But as stated, it's become more of an issue as people want the extra reputation points from edit suggestions.