The Inquirer has linked to the research of Prof. Renugopalakrishnan, who is doing some very interesting work with bacteria.  If you can handle the idea of literal bugs in your data, these disks will store a lot.  I wonder if as a side benefit, they will eat the crumbs and lint that always seem to end up in jewel cases.
“Professor V Renugopalakrishnan says his DVDs, with bugs pre-installed, can store more than 50 Terabytes of data which is enough to make computer hard disks obsolete. Renugopalakrishnan uses a light-activated protein found in the membrane of a salt marsh microbe Halobacterium Salinarum, which is better know to its friends as bacteriorhodopsin.

It captures and stores sunlight to convert it to chemical energy. When light shines on bacteriorhodopsin, it is converted to a series of intermediate molecules each with a unique shape and colour before returning to its ‘ground state’.”

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