I agree. I don't always buy AppleCare but when I do, I buy it directly from Apple. I have purchased it on my oldest G4 Mac Mini, Macbook, iPhone 4, and iPad but not for any of our newer Intel Mac Minis or iPod Touch's. I never have to dig for serial numbers or prove I'm not trying to commit a crime when I call Apple. I like dealing with Apple and paying full retail for AppleCare is a small price to pay for knowing I'm not being scammed. The one time I did need a repair for one of the kids' iPod Touches, it was a cracked screen and Applecare wouldn't have helped. When my iPod Touch died, it was within the normal warranty. When I got the reminder email to buy AppleCare, it was just before the new models (with camera, etc) were coming out and I decided I'd rather get a newer model if something were to go wrong in the future. You should weigh the (full retail) cost of AppleCare against simply paying for the repair or buying a new device, keeping in mind that all repairs aren't automatically covered.
One example of a scam involves selling the same number to a half dozen people on ebay so that by the time anyone finds out their AppleCare number is invalid, the paypal dispute window has closed. If you buy AppleCare from any source other than an Apple store, make sure you get a physical box that is unopened so you know you are the first person using the code.
Another nice part of buying Applecare directly from Apple at the time you purchase your Apple gear is the product registration is (often) automatic. I don't waste a second of my time typing in code numbers for AppleCare.
One thing to consider is that Apple products tend to hold up fairly well. You might not need Applecare on everything you buy. I recommend it for computers because things can go wrong years later and phone and genius bar help along with (most) repairs are free.