I've been editing some of the tags on the main site, and I noticed that a few (two out of the top twenty most-used tags) have links to Wikipedia, and one quoted directly from a Wikipedia article! In one case, the quote made up the majority of the tag wiki (and I left it there); in the other case, it was added as a supplement at the very end which I deleted because that tag wiki was clearly strong enough to stand on its own. The first tag had a poor tag wiki if the Wikipedia article is excluded; the second had a very good tag wiki.
Should we quote or add links from Wikipedia in our tag wikis? Should we use external sources at all?