Your blog is a way that you reveal a great deal of information to the outside world. The most important fact is that the constitutes of your blog is in fact Intellectual Property, which you own (if you don't copy others stuff :-)... ). According to WIPO, Intellectual property refers to creations of the mind: inventions, literary and artistic works, and symbols, names, images, and designs used in commerce. And, therefore, your blog deserves some legal respect if you are interested in securing ownership for your information.
But, the question is why a license is required. According to this article, a licensor may grant license under intellectual property to do something (such as copy software or use a patented invention) without fear of a claim of intellectual property infringement brought by the licensor.
Thus, the importance arises, if you are interested in claiming what you own (or in other words secure your intellectual property). Blog licensing can vary from a all rights reserved to no rights reserved. Technically, if you say nothing, depending on the Territory to which a IP infringement law is enforced, you have the chance of falling into somewhere between these two extremes.
Therefore, if you want to specifically allow, or disallow the way people interact with your information in a variety of forms, you might consider creating a your own blog license. However, there are lots of easily adoptable schemes, such as Creative Commons. This blog is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported license.
What ever scheme you may choose, the security of your information lies in the strength of the legal license document you present. You must consult a lawyer if your information requires severe protection, but in most cases a trusted third party (ex:- Creative Commons) might be helpful.