What makes libraries so important?

There is a growing #savelibraries campaign on Twitter. Why?
Recent political decisions in both the USA and the UK have put libraries under threat of closure through withdrawal of public funds. From a fundamental view of knowledge sharing and education this seems entirely wrong.

The obvious reason is that the accountants and politicians in their wisdom have decided that the cost of staffing libraries and maintaining the buildings does not produce a sufficient ‘return’. 

The world is going through an economic slump at present and it seems short sighted to reduce the level of education of the population. Libraries are a social centre where people go to explore new knowledge and deepen their existing understanding of subjects.

The issue of saving libraries is about far more than buildings full of books, it is affects society as a whole. Losing a single library devalues a community, to lose them more widely affects a whole nation.