False Consensus Effect

"It's called the false consensus effect, and what it means is that you've been cloistering yourself without realizing it. Labor too long and too hard at chasing the next Hot New Trend, intermingle with a bit too much energy and dedication with your own Circle Of Trust, and gradually alienate yourself from whoever might be outside that crowd; pretty soon, you'll become an expert on what everybody thinks, and you'll be chronically wrong."
-House of Eratosthenes