According to my recruiter's stats he told me that 93% of those that accepted counter-offers from their original company were looking for a job again within 6 months. The two scenarios were a) The company extended the counter offer to keep the employee long enough to carry out the contingency plan (i.e. hire someone to take his place and then fire the guy who they couldn't count on to stick around) or b) all the reasons why the guy wanted to quit are still there, except maybe the money one -- and rarely does someone quit solely over money. People will deal with less money if they love getting up and going to work in the morning.
