Techcrunch UK has a funny post about "Web Analytics Faux Pas" from guest author Ed Freyfogle.
Ed listed some common mistakes and two of them I've myself saw many times:
1. Confusion between Hits, Pageviews, Views, Visitors, Uniques, Users
2. Hyper-analytical environment.
Also not to forget the oppposite:
3. Companies that run Omniture or some other high-end analytics vendor, but don't really have someone to take care of it (or the person is not really interested since the company doesn't care about pageviews, but revenues)
Anyways...great read. Love the picture too. Reminded me of my "higher mathematics" class back in the college days.