I had another thought about testing: What about recording use cases of an application via a little program that watches your steps?

What does it do?
I could imagine such a program for web programs. It could very well be a Firefox Extension. It has two modes: Do nothing and Listen. The first would be the default, but when you are testing your web application or someone else does, turn the mode to "Listen".
Now the program records what you do. Type some text in form field X, click a button Y or hit a Link Z. Just as in recording Macros for Word processing programs, you could easily say where your use case starts and when it stops.
This way you could get a sequence of defined actions with no effort. Those action sequence represents a reproducable use case, just what you are looking for when you are heavily testing.
How easy could it get?
In fact, a way to save even more effort would be that the program always listens, and when you think: "Hey, I just had a case worth recording", you hit a button and the program makes a use case out of your last actions. This would be great for testers who test a zillion things and when something goes wrong, they could just produce a reproducable use case with one mouse click.
How would it work?
First the easy things: identifying the active elements of an application via mouse events is no big deal. Also not too hard would be making up a user interface where you can adjust the use case with no big trouble.
Now the difficult ones: For a use case that needs to be reproduced, you would need to know things about the environment on the computer that it was reported on. There may be a lot of work defining what would go into there and what not.