Some good points, its great if a business will allow you to set all their users workstations to run in non administrative mode, however its not an easy path to convince someone its worth the investment in time and energy.
You can actually run a workstation in this way without a virus scanner or spyware scanner and it will be quite safe.
What would be great is if programs were written with this in mind.
MYOB, Quickbooks, Office, and every second third party app you can think of requires administritive privileges, and even if you do give full user access to the folder the program resides in, you find later it needs administritive privilege for 10 other files scattered throughout the operating system.
Then the client goes to add a printer!!
Steam comes out of their ears as you try and show them how to right click and run as administrator, they scream "Just damn well take all this rubbish off, I want my pc back the way it was, I dont care if its insecure"
Is it their fault when things go wrong and they get a virus or spyware? Yes it is, will they blame you for the problems when they do occur? most likely.
If people did the right thing with their computers, there would be a lot of unemployed computer technicians.
One day computers will be as complicated as the average toaster, they break and you will buy a new one.
Applications will be simple and will reach a level of usability that cannot be surpassed.
Thats the day I become unemployed.....
Now you opened the door to computer quotes

I like quotes especially Microsoft ones.
"640 K ought to be enough for anybody."
-- Bill Gates, 1981
"The best way to prepare [to be a programmer] is to write programs, and to study great programs that other people have written. In my case, I went to the garbage cans at the Computer Science Center and I fished out listings of their operating systems." -- Bill Gates, OS/2 Notebook, Microsoft Press, 1990
"Microsoft's biggest and most dangerous contribution to the software industry may be the degree to which it has lowered user expectations."
-- Esther Schindler, OS/2 Magazine
"Microsoft Products are Generally Bug Free"
-- Bill Gates