I just ran across a formal paper expanding on this idea, complete with a salt, a threat model etc.  See their demo and abstract submitted to
 FC'12 : Financial Cryptography 2012
 http://fc12.ifca.ai/:

Jeremy Clark & Aleks Essex -a demonstration of a simplified version of CommitCoin
 http://people.scs.carleton.ca/~clark/commitcoin/

CommitCoin: Commitments with Temporal Dispute Resolution using Bitcoin
 http://people.scs.carleton.ca/~clark/commitcoin/abstract.pdf

and the commitment itself:

 http://blockexplorer.com/tx/2993c284f0b6838386ddd286af415384560d93cc4e27d25087fd6534f8e0d276

I agree that it is probably better to mix various uses in one block chain which can then be optimized, rather than trying to establish and defend multiple block chains for different purposes.