The boss, the VC or the customer is ultimately people you have commitments to. You can always decide not to comply to their request and see what happens. If your product is great, the customer might frown but will stay, and you'll be fine. The same thing with your boss, if you're a stellar employee, your boss won't be pleased but your job will probably be safe. In any case, you measure and take risks. The main difference in my opinion is you see your boss almost everyday, she gives you guidance and tells you if things go bad. With customers, you have to proactively get the feedback, or anticipate their needs.