Coffeehouses were especially important to the spread of knowledge during the Enlightenment because they created a unique environment in which people from many different walks of life gathered and shared ideas. They were frequently criticized by nobles who feared the possibility of an environment in which class and its accompanying titles and privileges were disregarded. Such an environment was especially intimidating to monarchs who derived much of their power from the disparity between classes of people. If classes were to join together under the influence of Enlightenment thinking, they might recognize the all-encompassing oppression and abuses of their monarchs and, because of their size, might be able to carry out successful revolts. Monarchs also resented the idea of their subjects convening as one to discuss political matters, especially those concerning foreign affairs - rulers thought political affairs to be their business only, a result of their supposed divine right to rule. 
Which venue created a unique environment in which people from many different walks of life could gather and share ideas?
Coffeehouses