All close to Obongo sign a anti-disclosure statement which puts them immediately in jail if they disclose anything specific that would either be an embarrassment, or even something good about Obongo. Look at the Benghazi folks who were forced to sign anti-disclosure statements.
The regime couldn't have possibly tracked down every single person Obama ever knew, and forced them to sign a non-disclosure agreement. There's no way the empty headed choom smoker could have even remembered everyone he ever knew.
Someone out there has to know something about the guy. Still, it's pretty odd that few outside of Jeremiah Wright, Moochelle, and Bill Ayers claim to have known him before 2007. I'd have to agree with you that a whole lot of people have been silenced.