I've tried a few here and there, its a great concept that just never pans out on the table.
I prefer individual scenarios, rather then ones linked to a prior game - and since these are usually team things - I ended up with a net determent in the next game thanks to my team mates performances!
Not to mention the inherent issues of getting people together, the shear amount of time and behind the sense work...and I think the biggest reason is that fluff and game play never match - so trying to make it make in a campaign feels very self defeating. IE a story is a story and a game is a game!