A lot of people comment that knowledge isn't like money because I can give you knowledge and still keep it myself. Most recently I heard this in a presentation from Loraine Ricino of Siemens where they had a quote from an exec in a promotional video "If I give you an idea and you give me an idea, then we each have 2 ideas, its that simple!". True, but it doesn't mean its cost-free.

"What information consumes is rather obvious: it consumes the attention of the recipient. Hence a wealth of information creates a poverty of attention" - Herb Simon.