[kogir]

Simple: If you can land a better paying (don't forget stock grants and options) and/or more fun job elsewhere, then yes.

Interview at other places you'd actually consider working and get offer letters. Compare.

As an employer, I knew my employees were doing this - It's my job to keep them, not their job to forego better opportunities and pay in the name of loyalty.

That said, if you do get better offers, talk to your current employer before jumping ship. They're best positioned to know exactly how valuable you are and might work very hard to keep you.