[Joeri]

Definitely not true, i have doubled my salary at my current employer through a combination of negotiation and normal pay raises. I never explicitly threatened to walk out, but i did point out when i was substantially below market rate, and that was enough.

I do think that overall switching employers makes it easier to get a raise, because a current employer is more likely to know your true market rate making it harder to convince them to pay you above that, or even at that rate (with them figuring you won't leave for a small difference).

You do have to be careful not to become a 'job hopper'. When i see a resume where somebody never stayed somewhere more than 18 months i'll figure we won't be any different and am less inclined to give a thumbs up to HR if that person needs a sizeable training investment from my part.