It seems to me that most of the people I hear recommend 3,000 mile oil changes are in the auto repair business. They see the results of lacadaisacle(sp?) oil changing. They also are in a business where neglected engines bring them more business, but they point out the advantage of frequent oil changes anyway.
If you drive a few thousand miles a year and trade cars often, I guess you don't need to worry about changing oil very often. If you drive a lot and want to wring the most out of your engine, it's difficult to change it too often.
Also, the main advantage to high quality oil, is the care and attention paid to additives. The cheaper brands don't have additives in as much quantity or quality to keep the inside of your engine clean, as well as other important things. If you use cheap oil, you could probably do quite well with it, if you were to change it often. Quality oil, changed frequently is proven to be the best engine insurance.
Change oil hot, and change oil often,
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in