Thanks to my colleague, Kathy West, for pointing out this article in Business Week. At the University of Alberta Libraries, we've been concerned with preservation for some time now, and have been using ArchiveIt to archive materials on the web that we've identified as priorities.
The Disappearing Web: Decay Is Eating Our History
Here's the research study mentioned in the article:
Losing My Revolution: How Many Resources Shared on Social Media Have Been Lost?
Bottom line from the authors: " From this model we conclude that after the first year of publishing, nearly 11% of shared resources will be lost and after that we will continue to lose 0.02% per day."