I saw a great write up by Pete6 over at CB with respect to how betas leak. Since a lot of people have asked this question figured I share with everyone a very clear and well written piece on this subject.
1. RIM release their proprietary software to their beta testers as they wish and when they wish. RIM OWN the OS so it's theirs to do with as they see fit. They also release these builds to different Partners and ISV's.
2. Beta OSs are leaked by what we may call RIM's beta testers or Partners.. These people have signed NDAs secifically saying that they will not do this. So be thankful that you see them at all. For if these people are caught they could be in serious trouble as I am sure that there are stiff penalty clauses in the NDAs.
3. RIM do read these forums but we constitute such a tiny amount of their user base (13 million phones, 500K on CrackBerry) that we are scarcely worth a blink from them.
4. RIM know what they have put in any given OS. After all, they wrote the code. Why do they need to look at us for what is wrong. Their beta testers are told what changes have been made and what to look for. They tell RIM what happened in extended use.
5. There are differences between beta OSs and carrier releases of the same number. However these are NOT functional differences. Everyone knows that you do not need to delete the Vendor.xml file in a beta OS but you do if you have one carrier's released OS and wish to install it on a different carrier's phone. Also carriers may ask to have their latest theme changes included in their final release. Therefore OS 4.7.0.xxx will be functionally the same worldwide but the beta file may be somewhat different from the carrier release due to what I just said.
6. If you see beta OS releases coming in rapid sucession then you may be sure that there are problems with the base product. We went through this with OS 4.5.0 for the Curves. It was a nighmare because there were 4 Curve models to contend with. OSs were come about one a week at one point. There were all sorts of problems. Now, six months later we have a very stable product.
I really hope that this post will finally dispel some of the myth surrounding beta OSs.