2. Having a strong belief that most non-programmers are dumb, including marketing/sales/customer service. This shows up when you interact with those folks. All the guys I've fired in my company are for this reason and never for their failure to not being able to implement an LSM based k/v store.

3. Asking for vacation with reason ("there is nothing to do at the moment"), then after returning from vacation telling us that the service got hacked because "I did not have enough time to fix that particular issue"

4. Failing to understand how the company makes money and our expectations. Some devs love their craft and take home big salaries but in office, they are busy painting us as a con show. Some part of your income comes from the effort of that sales guy/gal, how is your work purer than her? Why paint him as a shady gal in the office?

5. I doubled compensation of some developers, they came back with a request to switch them from fulltime to parttime.

This is based on early experience as a founder.