Oil change interval depends on the type of driving that you do. People that consistantly drive in city "stop and go" and lengthy idle situations need to change their oil more frequently than those that primarily do only highway type driving. Further vehicles that pull trailers, campers, or carry heavy loads should change oil more frequently.
Folks living in "dusty" environments needn't worry that their oil change interval be altered for the locale, as crankcases have been sealed from outside contamination for at least a decade. However dusty areas tend to be hot, and vehicle operation in hot climatic conditions should be considered by shortening the interval, as well as using a slightly heavier viscosity oil. Your owners manual should give you a chart to guide you in oil viscosity selection as well as interval.
For the folks that change their oil every 3000 miles regardless of conditions, you can't really go wrong, and basically I consider this practice "cheap insurance" against premature engine problems. Using a good quality oil is nearly as important as changing it frequently......I have always been a big fan of oils that are manufactured from Pennsylvania crude, due to the unique structure of the molecules and their properties, but most brand-name oils are quite good.
Don't forget that automatic transmissions require lubricant changes as well as the engine......and anyone that has had to replace/rebuild their transmission will attest that it is nearly as expensive as replacing the engine. Transmission fluid should be changed at least every 30,000 miles......and more frequently if you pull trailers, or carry heavy loads. It is easy to check the condition of your transmission fluid.....just pull the dipstick out and "smell" the fluid. If it appears brown in color, and smells "burnt", or like it has been hot.....replace it ASAP.
Rear axle/transaxle/transfer case lubricant should also be changed periodically.....I like to do it every 50,000 miles.......although these assemblies are "sealed systems", the lubricant picks up filings and burrs from the gears, and unless it is changed occasionally, wear will increase.
The general rule that I always use is "oil is cheap", repairs are not.....and as far as the quoted OP comment is concerned.....screw California........the state isn't going to pony up if one of their citizens blows an engine due to failed lubrication.
doc