I'm in several beta programs (including the software I write for a job of course).
Beta testing is not just having access to cool new software, it's serious (and often incredibly boring and frustrating) work.
Microsoft wants only people they know they can trust to keep their mouths shut and to really work at it in their beta programs, an attitude I think is perfectly correct.
by knowing developers :)
That's the nice thing of online communities, people who know their stuff can get noticed by the developers of a product.
That's how I got in contact with several, leading to places on beta teams and vollunteer work as a customer support person for one company (with free access to their entire product line as a reward).