What is an information snob?

Someone that holds information you would like but would prefer to be blatantly unhelpful so you continually need to try again to get their help.  It's sort of an odd co-dependency relationship - they are desperate to show people how smart they are but they hold knowledge no one really cares about. 

Fearing a loss of superiority, they have to be vague and cryptic so you keep interacting with them.