All the time you hear about smart, gets-shit-done types that can take your company to the next level, or the opposite, the non-productive, not as smart, jerks or assholes that could be detrimental to your startup.

What is 1000 times more insidious is very smart, insecure people. You hire people like that and they'd destroy your company from the inside, because they're (probably) affable, do good work and are so good at navigating internal politics that if you're not paying attention they can chase off the type of people you need and quietly toxify your culture without you noticing it.

The problem is that they are out of their depth, but are not used to failure, so they will do anything to avoid looking like they have failed at anything, including abiding criticism, or engaging in things they're unfamiliar with. If you put them in positions of power. Good Night, and good luck.