It really depends on what sort of software you are writing. If you are writing user interface code, there are many different ways a user can screw up your prog

It really depends on what sort of software you are writing. If you are writing user interface code, there are many different ways a user can screw up your program. Maybe they are holding down "alt" while right-clicking and dragging to highlight half of a misspelled word. In this situation, you really need a lot of testers. And this is a lot of what Microsoft does, local applications like Office and the operating system itself. By contrast, websites avoid a lot of this sort of testing. You don't have to test what happens if a user clicks on a link in a strange way - that's the responsibility of the browser. Or if you work on a part of the Google search engine, you can replay query traffic to see if it crashes. That will test a heck of a lot more corner cases than any tester. With web-delivered services you can also fix glitches as you find them, which minimizes the cost of missing a bug.