Wikipedia uses the wrong criterion. Instead of asking of an article, "Is this notable?" they should ask "Is this useful?" If so, let it remain. This is much more elegant than their already large body of law (http://en.wikipedia.org/wiki/Category:Wikipedia_notability_g...) and precedent (http://en.wikipedia.org/wiki/Special:Log/delete). It works for edits too; you just ask, "Does this edit add or subtract utility?"

The usefulness criterion would allow promotional articles and edits. Automated spam should still be deleted, but promotional handwritten stuff that contains some facts is better than nothing. Subsequent edits can remove the spamminess.

Of course, this means an article on any topic is OK. In a web encyclopedia, that's the right thing.