On that note, I'm in a campaign that has covered 2.5 years of game time in roughly the same time of real time. We've had seven combats total.
In the campaign I run the game has run for over a year and has had two, plus it's only covered about a week of actual game play, and this isn't because the game runs slow on posting, some of the players post several times a day, it's just that everything matters in the game, even the inflection of how the characters speak to each other.
I think giving out lots of combat is bad for a story because it encourages hack and slash play that is more about equipment lists and stats than about a plot with interesting and believable characters (obviously a preference), plus, combat is dangerous! Who wants to provoke a fight if it means taking a sword to the chest? Not I. Obviously that has a lot to do with how cinematic the setting is, but also I feel combat is bad for PbP because it takes so damn long.
If people want some quick hack and slash action I recommend shelling out 15 bux a month for warhammer online as it gives you shiney animations to boot that you don't get on MW. This place is more naturally conducive to that which you cannot do with a video game: Tell a story without a linear plot.
Video games may have bright graphics and all the hack and slash tits and explosions you can handle, but MW has the distinct advantage of not being frozen in time so that the story can evolve, this is something you can't do with an MMO. EVE online made a valiant effort, but even then it paled in comparison to the possibilities of MW which allows that the sky is the limit.