Unless you are able to stand there and physically watch what they are doing you really can't and at most dealerships that is impossible since the service area is back in the bowels of the building. If you go to a quick lube, WM or your local service station you can probably stand there and watch since the service bays are generally open. Your concern here along with a plethora of other things such as them putting a filter on SO TIGHT only a 600lb gorilla can wrench it off, or cross threading the filter, and the list is never ending. IMO it's just so much easier to do it yourself and then you know it's done right and with care and you will save a few bucks in the end that one should seriously consider that option. With some exceptions I think doing as much as you can yourself is a good idea and the few tools/items you need for that except if you want a set of car ramps will easily be paid for within a few oil changes. You have to remember the ultimate goals of a business based service provider is to make $$$ and not to provide you with the best service, but the minimal so as to not hurt their profits.
Most places you cannot because of liability concerns.
This is a pretty ignorant generalization. Most of the jobs I've worked have been service based and I can say the customer was always number one. Every company I've worked for always had a strong emphasis on providing excellent service. And do you know why? Because if we didn't, we wouldn't have any customers. Granted there are companies like Walmart that could care less about customer service, but not all companies are like that. In fact, most are far from it.
You are entitled to your opinion and it's no generalization that business prime focus is on the bottom line and the stockholders prove that. I view not understanding that as being naive and uninformed. Remember I was talking about Businesses and not what an individual might or might not do and the worry expressed in this thread and the recent threads on the "Fluff" being added on when the members are having routine service done is proof enough to demonstrate my point.
What's to say they wouldn't grab one out of the trash can and shelve the stuff you brought in?
Of course it is and I acknowledged that fact in my original post w/o customers there are no profits.
If you are using the some standard oil brand (Penz, M1, Quaker, etc) then yeah they could. Also, you could mark your bottle (I do this whenever I go in for recalls to make sure they actually replace the part) and then see if they try to give you the flim-flam.
