Inspiration comes regularly from YouTube. And consumer generated content doesn't just mean 13 year olds with Handycams, you also get some pretty slick stuff too.
The excellent Zero Influence has posted a great piece on mapping interestingness over time citing a recent Yahoo patent filing. In order to prevent a self fullfilling prophecy of the good stuff staying at the top, a natural erosion should occur over time:
“For example, the system designer may set up the score computation to decrement the thus-far accumulated score by a predetermined percentage over time starting at the time the media object was posted. For example, this time decay may cause the score to decrement by 2% per day from the day of posting. This and other means may be employed to prevent the occurrence of “positive feedback loops” where the sorting of media objects by interestingness itself skews the results, causing those same media objects to be more frequently accessed, thereby unnaturally increasing their interestingness scores.”