Tony, With a shelf in place, they can quickly jump on an opportunity, say if the pps zooms up after some good news, they can do a financing very fast to take advantage of it.
As I recall, in 2006 or 07 they put a shelf in place, though I don't recall the actual amount that was made available. The amount was depleted by the 8-07 PIPE, so this new shelf (assuming that's what it is) would boost the amount available back up again.