is there any evidence or possibility that this is actually done in biology already? If DNA is writable, then cells have a Von Neumann architecture!

This is somewhat like the way antibodies are formed. There are genetic changes (recombination) at the DNA level in the antibody hyper-variable regions. This is how we produce antibodies for everything based on a single gene (somewhat).

However, antibody VDJ recombination is more akin to write-only memory. Once it is produced, it doesn't change.

Googling keywords like non-coding RNA, reverse transcriptase, and epigenetics suggests that even further back than this article, this was suspected to be the case.

So, if I understand this correctly, it's like Johnny Mnemonic, but you don't have to store the data only in your brain. I bet if you used your entire skin instead of just your brain, you could store a whopping 500 gigabytes!

Joe Davis has been encoding data into DNA for some time.

http://www.viewingspace.com/genetics_culture/pages_genetics_... http://en.wikipedia.org/wiki/Joe_Davis_(artist)

I wonder what the equivalent of "rm -rf /" is in that environment? :)

Probably http://en.wikipedia.org/wiki/Apoptosis

That's more like taking a hammer to your hard disk. What we want is more of a virus that rewrites your genome with a single base.

Obligatory Dresden Codak link: http://dresdencodak.com/2009/07/12/fabulous-prizes/