Computer Science: Don't take counter-offers from your job

"Be Careful of Counteroffers"
Network World, January 17

Steve Hall, the director of recruiting at South Carolina-based
professional search firm Find GreatPeople International, explains why
highly-qualified IT professionals should think twice before accepting a
counteroffer from their current employer. As Hall points out, accepting a
counteroffer - no matter how attractive - could jeopardize one's future career
or destabilize relationships with peers if not done properly.By working through
a number of worst-case scenarios that might play out if an employee decides to
stay with his or her current employer, Hall illustrates why counteroffers may be
dangerous for future career growth. After all, "a resignation is the business
equivalent of holding your boss at gunpoint," so even if an employee winds up
with a promotion or more money as a result, the culture of the company will be
changed forever. In addition, by accepting a counteroffer, an employee will
implicitly change the expectation levels for future performance, meaning even
minor missteps or miscalculations will be magnified. Even worse, the act of
presenting a boss with the chance to make a counteroffer might be misconstrued
as an act of corporate disloyalty, says Hall. It's important to address any
misgivings and dissatisfactions with the boss before announcing a decision to
consider employment elsewhere: this gives the company a fair chance to rectify
them without jeopardizing your future career.

http://www.nwfusion.com/careers/2005/011705man.html

So basically don't take a counter offer at your job, because it will change the culture of your company by making your co-workers hate you, you will raise their expectations of you, and you will not be trusted by the company to stay.