So according to Brewster Kahle's estimates for storing all US phone calls (http://blog.archive.org/2013/06/15/cost-to-store-all-us-phon...), it would only take 272 of these theoretical DVDs per year!

Of course there's a big tradeoff in latency (on the order of 10s of seconds to switch DVDs) and throughput (unknown), but properly indexed I'm sure it would still be extremely useful, and extremely cheap.

Imagine fitting all of that data in this little box: http://gizmodo.com/5321357/sony-finally-popping-400+disc-blu...