Michael L. Nelson discusses challenges in web archiving at the Web Archiving Cooperative at Stanford in September 2010. He notes that while the web from 5 years ago is well archived, the current web and shadow webs are not well archived. Archiving should be a service with short-term utility. Ajax content, personalized pages, mobile sites, linked data, and social media are among the types of shadow web content not well archived currently. Batch and real-time recovery systems could help address these gaps.