Jordan S. Hatcher is, among other things, a lawyer, academic, and entrepreneur working on Intellectual Property and Internet law issues in the UK and worldwide. He is heavily involved in the Open Data Commons initiative. Last month he gave me an interview on IPR issues associated with data licensing. His brief answer to the question why data needs a seperate licensing framework:

The answer to me is that database and data are different.  They’re different legally and different practically in what consumers and producers of open data want to do with it.  They’re also different in what the future looks like in terms of things like linked data.

Read the details in the full interview.