I've seen a bunch of approved tag wikis and excerpts that really, really don't follow any of the guidelines for Tag wiki's/excerpt and are run of the mill man/wikipedia/project page dumps. This is not useful, but the worst part is that there are people approving them and the editor thinks he's doing a good job, 'cuz, hey! they are getting approved!
I would ask that to the ones writing a tag wiki or excerpt, if you need to copy and paste something from the internet and nothing else, please, abstain from doing so. Also, Reviewers, please review. If you see an unhelpful suggestion, you can reject for:
This edit does not follow any of our tag wiki guidelines and is unlikely to help instruct future visitors in the appropriate use of the tag
If you find copied content without proper attribution:
This edit plagiarizes content from an external source without proper attribution.
Remember that tag wikis are the elevator pitches of the tag.