[Jane Mayer for *The New Yorker*][1]:
> “The public doesn’t understand,” she {Susan Landau} told me, speaking about so-called metadata. “It’s much more intrusive than content.” She explained that the government can learn immense amounts of proprietary information by studying “who you call, and who they call. If you can track that, you know exactly what is happening—you don’t need the content.”
Mayer also points out that when you are looking at just metadata the operation effectively becomes a data driven collection, whereby computers do all the heavy lifting. This means the NSA can effectively monitor every communication with minimal manpower. Yikes.
[1]: http://www.newyorker.com/online/blogs/newsdesk/2013/06/verizon-nsa-metadata-surveillance-problem.html?mobify=0