But we can study these libraries and decide whether or not to trust them.
Those "trade secrets" often contain algorithms taken from FOSS or ripped from other companies' software.
I guess this issue will only be over once IT businesses will be obliged (by regulations or by natural selection — time will tell) to sell real work, not thin air in the shape of binary copies and license keys.
But the sad truth is, more and more companies just use this "trade secrets" excuse to conceal their own (or govt-issued, who knows) malware in their products. Oftentimes, they don't even try to hide this in their EULAs, which basically say "once you install this on your computer, it's no longer yours but ours".
Many Faildows users still don't realize how large of a technogenic catastrophe this could cause if M$ decides to flip the switch.