This largely depends on the content type.
In his Alertbox, Nielsen leaves out my only reason why I would leave out a byline from a news article: If the content is impersonal (i.e. when users don't care at all who wrote it).
Of course, determining whether content is impersonal is a subjective process. It is pretty easy to determine that plain news articles on CNN.com are impersonal because CNN is a large news organization. The byline can go at the bottom. However, what about your local newspaper? If it is the same 5-10 authors every day, then each article is inherently more personal. Opinion pieces and reviews (as mentioned by Nielsen) are even more personal.
For most articles, a short byline should be at the top of the article and a longer bio should be provided at the footer. The footer bio should link to the full bio (if available on the site).
J. Jeffryes's points about looking lazy and helping users discover more content are good, too. Tajmo's argument for consistency is a good one and why I would not eliminate the byline for mobile.