<del>RJT - I like to see an option to enable awarding a list of prizes to random unique (registered) users, providing there's enough safeguards to prevent false or bot clicks - registering only 1 entry (click) per unique per 12 or 24 hours.
I also like the idea of offering the ability to share ad revenue with users like Armyn's suggestions. Implement code in the same user accounts as a admin option to let users input their Google Adsense PubID which would then be rotated in with the shortURL's google adsense ID as the admin set percentage value 10/90%, 20/80%, 30/70%, etc. Similiar to various forums that share ad revenue with active users.
Last but not least, the "bundled" ShortURL's feature sites like Bit.ly implemented is pretty cool and gives more of an opportunity for a summary page with advertising. Letting users enter multiple URL's into one ShortURL to share, and visitors seeing a summary with the ability to share, and vote on the links, or copy the bundle and make their own version.</del>