Rapid Prototyping and Development--Questions

I've been thinking again about rapid prototyping and RAD tools for Web development. Perhaps it is because I have been working with Enterprise apps for a few years, with their focus on hard-core non-functional requirements (security, scalability), but I don't see much going on anymore. It seems to me that J2EE, and the various Java frameworks, are so focused on robustness and maintainability that rapid prototyping is nearly impossible.

In the wild and whacky early days of Web development, it seemed that we got the functional requirements right, but then endured hell when our applications didn't perform or missed the mark on non-functional requirements. Why? Because we did very minimal requirements and immediately dived into scripting pages, essentially rapid prototyping. Now, as I see it, the Web world has inverted this situation: we have to do more requirements because it is more expensive to get working code in front of the user, but the technologies are more robust. I contend that, in general, it has become more difficult to get the functionality right, and that we now have applications that are often over-engineered.

I'd like to figure out how to re-introduce rapid prototyping into the realm of Java Web development. Here is what I think I need to figure out:

• I see a few essential ingredients necessary for rapid prototyping: Fast and simple development of presentation code, automation of basic CRUD activities, and quick develop/run cycles. What else?
• Are there Java technologies that allow developers to skip the enterprise stuff initially, and add it in later with a little refactoring?
• Are non-Java tools, e.g. Ruby/RAILs, that allow for development that is so inexpensive that we are willing to throw it away?