I think lack of votes is in part due to the content of the pipe; alot of recent posts don't interest me, but not to the point of voting down either. In the past the pipe has been quite a bit more active (vote-wise), but now that the pipe is filling up, it has the wall-of-text feel, i think its easy to become disinterested and drift away.

That said, I feel its important for there to be an indicator on the homepage as to how many stories are currently in the pipe. Talk of a notification system makes me believe this will be an eventuality.