Open data is flavour of the month at the moment, with tim berners lee unveiling the goverments open data initiative. people are starting to look at what can be done with the data, for example: i'm interested in the cost/benefit of making the data available.

Firstly I have to admit that despite knowing that "data" applies to text as well as numbers I always think of open data as statistical reports, but thats my preconception and I'm battling it. So anyway …

It is good to be open. and openness is better than secrecy. but what is the amount of effort required to make data open, versus the actual use of that data?

Looking for a parallel, I thought of Freedom of Information legislation. For that FoI legislation, it is cost-effective to have a publications schedule rather than have to respond to each request for information. so, aside from the avoiding-writing-it-down tactic, it's in an organisation's interests to be more open with their key documentation than they used to be.

Is open data a similar change in the behaviour of organisations? And do the cost/benefits weigh up? What's the effort required, for example, to anonymise data so that it can be shared without breaching data protection rules? For example, if someone in every local council has to spend on average a day a week cleansing data for release, (at the taxpayers expense), does that data yield useful benefits to them? how long will it take for the benefits to be seen? 

Or is it just about openness vs secrecy, as an expression of the value of transparency above any real utility?

Interested to hear the evidence on cost/benefit …