If the blockchain a currency or token is on is only as strong as it's developers, then what is the best way to really find out how to trust it before investing? Especially if the developers are anonymous?
Presumably you're not going to put money into closed source? If you do then you get all you deserve.
As for open source it's voluntary all the way down the line. A developer puts out code, miners run it, buyers buy their product. Everyone examines the code for viability. No one does anything with it if it's not good enough.
It doesn't matter who put the code out or what their name is. The only thing that counts for anything is the code itself.
If the code is shit then no one mines it and no one buys it. If an anon developer puts out shit code on an existing project then miners reject it and stick to the code that works, and more than likely a better developer picks it up.
That's the entire point of crypto.