May be used at the end of an article to warn the reader that the written material has not been personally written by the author. He or she probably dictated it to a secretary, but they did not have the time to write it themselves. Very busy people may be expected to sign off of their article with such notation. In general, it may be regarded as disrespectful, especially when the writer is not busy.
Commonly used to sign off on correspondence where formality takes a backseat to speedy communications, or where such correspondence is routine. When this is not the case, it is a discourtesy to the recipient of the letter.1
This practice is used often within the medical community, though its appropriateness is still debated.²
References:1How to Win Friends and Influence People, by Dale Carnegie²BMJ (British Medical Journal)