Brod didn't destroy it. He published some (including The Trial, The Castle and Amerika), but kept a lot back, stored in suitcases, which was supposedly a compromise between destroying and publishing. After his death it went to his secretary, Esther Hoffe, and then when she died (aged 101) in 2007 it was inherited by her daughters Eva and Ruth.
Now the remaining material is to be sold, but there is a bizarre twist, as recounted in the London Review of Books:
What no one could have predicted, however, is that a trial would eventually take place after Esther’s death in which her daughters, Eva and Ruth, would claim that no one needs to inventory the materials and that the value of the manuscripts should be determined by their weight – quite literally, by what they weigh. As one of the attorneys representing Hoffe’s estate explained: ‘If we get an agreement, the material will be offered for sale as a single entity, in one package. It will be sold by weight … They’ll say: “There’s a kilogram of papers here, the highest bidder will be able to approach and see what’s there.”Butler goes on to discuss the wonderfully convoluted arguments as to where the material ought to go, taking in issues of Kafka's identity and ideas in his writing. (The article is available free on the LRB's website so you can read it all online). However, the specific information angle I wanted to flag here is in a letter about it that appeared in the next issue:
"Who owns Kafka" Judith Butler LRB 3 March 2011
Assuming it were in his or her power, a presiding judge could make it a condition of ownership that the entire archive, every last scrap of it, be digitised and made freely available in suitable downloadable format over the internet. Anyone, anywhere could then construct a personalised version of the archive, organised in any way they saw fit. The physical location of the original material would become a matter of little importance, of interest only to paper fetishists and the odd forensic scientist, for goodness knows what arcane research project. More properly, the papers themselves would be destroyed once digitisation were complete, finally honouring Kafka’s wishes, and leaving the work itself truly weg von hier, for if anywhere meets the conditions of a destination that, as Judith Butler puts it, is not a place as we know a place to be, it is surely cyberspace, or whatever we choose to call it these days.I'm sure you can see the information angles, but I'm thinking particularly of Katherine Hales' "Information has lost it's body". Does destroying the body honour Kafka's wishes? (And I wonder whether I'm a "paper fetishist"!)
Martin Jenkins LRB 17th March
Update 7 April, the papers have been jointly purchased by Oxford's Bodleian library and the Deutsches Literaturarchiv (German Literary Archive) in Marbach (http://www.guardian.co.uk/books/2011/apr/04/kafka-letters-oxford-german-literary-archive)