Several people have mentioned that spotting isn't important because of GPS. My question is who is programming the GPS? Obviously the pilot. Ever been on a flight with a "new" jump pilot? I have. Ever seen a GPS unit lose signal or power? I have.
Understanding where YOU are going to deploy, where you are in exit order, what the winds are doing at all levels, and what your group's fall rate through those winds is ALL play into your spot.
The first guys out need to be ahead of the "perfect" spot so everyone can get out in time to get back. The last ones out will be behind, while the guys in the middle get the best spot. Unless, of course, you are planning a high-pull or going dirty low or tracking or wingsuiting.
The spot your pilot gives you is a good general spot, but when you're doing something a little different, communicate with your pilot. At the end of the day, it is YOUR responsibility to check the winds (do you know where they are posted?), know your fall rate and canopy descent rate through them and get out in a safe spot.
That green light means the pilot has made his best estimation and the plane is ready and safe for you to exit.
Learn how to spot well. It could save your butt ...and canopy ...and container, and teeth...