Corps have always had semi-regular Runners that they would keep tabs on and work with, going back to 1st edition even. It was just less common to see that in places like Seattle.
It was an interesting idea, and a change of pace from the regular Shadowrun Style, which I think was cool. I like stepping out and doing something a little bit different. Plus it was a way to get cool rewards and to have personal "side missions" for various characters. In theory, it added depth. But, it also added complexity to the games, and that made things get a little wonky sometimes.
That's one reason we're dropping affiliations and switching to a vastly simplified Faction system (More on that soon, I hope!)
Bull