I'm reminded of this recent post by James Fee, talking about geodata, but I think it applies to the general case: "... The question was APIs or downloads... Personally, I believe [data] is one of the best ways for citizens to keep track of their government (local to federal) ... APIs tend to deliver what their “owners” want them to do. Raw data means everyone has an opportunity to check each other’s work. Of course,…
Instead, a good API makes government into a platform for free (and paid) services to be built to deliver that data in innovative ways. Examples of this are starting to appear in places like Chicago which has opened up a lot of data access – for things including transit (bus tracking, etc.) and a lot more. Giving hackers platforms to innovate will definitely yield better results than just throwing gobs of data at the general public. (Never mind that not all raw data is created equal or that raw data also requires savvy people to distill.
It also means that it's potentially going to be easier for one unit of government to interact with (or at least query) another. That may be big as well.