Here's an article that sheds some light on the subject, at least for me. Be sure to read the comments.
http://www.digitalmusicnews.com/permalink/2014/03/28/madashellgetty

A couple of things weren't brought up is this. Pump Audio (like other libraries) doesn't notify the composer at the time of licensing. The only way you know is when you actually get paid. That leaves the composer totally out of the negotiation process, so you could virtually be giving your music away for pennies royalty free.

What do the PRO's think of this?