Why QA should be involved in the earlier stage of software life cycle?

What are some of the good reason for QA to get involved in the earlier stages of software development life cycle?

I have some ideas...like...

it helps them to get more knowledge about the product and come up with good test plan/test cases...

What else?

At least from my experience a lot of times the code needs to be designed and written so it can easily be tested in an automated way. I have dealt a lot with embedded software like cell phones and it is almost impossible to create a machine to push buttons effectively on all cell phones. It is better to have an interface into the phone that can simulate a key press to test the software above it.

Similarly for very complicated pieces of software it may make since to design interfaces/hooks to where test programs can attach into the software rather then trying to put them in at the end.

QAs have more knowledge of Domain regarding any project as compared to Developers in huge projects and they can give some really good suggestions regarding the UI, Flow and specifications of the documents. Plus your reason. Plus QA can assure the quality of each document produced as the result of each acivity eg. Requirements Document, Spec Document and so on.

Wait - do you mean "quality analysis", or "question an answers"?
For "questions and answers":
The hardest part about a software development project is finding out what the clients REALLY want. Often times, it is easy to think "oh, they want this" and develop an entire solution to find out that what they really wanted was something completely different. More time spent in Q and A
on the front end greatly reduces rewrites and dissatisfaction on the back end.
For quality assurance :
Hmmm.... not really sure about that. I mean, obviously you want to be sure you are using shop standards for coding, creating secure code, using proper naming conventions, etc. Of course, I am being arrogant here - forgive me. I am skewed because I am a programmer, and I always think everyone in IT should know that, but it is not the business analysts job to know that.

Members of your QA team often have a the best understanding of the requirements of your system environment. They can help to avoid specifications that will make the new system incompatible with other systems that will need to work with your system. They will know system level requirements for all systems that need to be incorporated in any design.

For example, your environment may require backup of data. Determining the correct specification of backup requirements needs to know what QA requires for audit and security (for example encryption of all personal information) to avoid having backup data breaking disclosure laws. Knowing the QA requirements is essential to ensure that they are met as soon as possible in the design stage.