The Watcher and Green Lanterns

I haven't read too many issues featuring new Green Lanterns Simon Baz and Jessica Cruz, but I have to say I really like the costume designs for each.  Cruz' personality and how it relates to her use of the ring is pretty interesting as well.  I am curious as to whether there is a story reason that Earth now has seven human Green Lanterns in operation (Hal, John, Kyle, Guy, Simon Jessica and the new Teen Lantern).  I don't think there have been so many at once before.