While reviewing some things I stumbled across this edit: http://stackoverflow.com/revisions/11565303/2
I approved, but I wonder, should the sources be kept in in the current format, or deleted?
Think of a tag wiki as writing an essay, except many people can contribute to it. It's nice to have plenty of information, and the more relevant information you can put into it, the better. However, just information can be as detrimental as no information. How do I know all this information is correct? That's what sources are for, and I'd be somewhat suspicious if there were an abundant amount of information with absolutely no links to external articles to verify it. They're not necessary here, but they're certainly allowed and I would personally encourage them whenever possible.
However, there's a difference between adding a source and plagiarizing, which that specific edit does. The entire context there is just a copy off the home page of the first link. We don't copy content here, and there's certainly no professor who would appreciate you just copying snippets from sites then listing them all in the sources. Be careful to check small snippets like that which sound like an intro off a product page and make sure it's not just copied content.