Over 20% of writers surveyed by PEN reported that they avoided writing about certain topics because they knew about surveillance.

That survey was in Scotland. Here are some reports:

One participant who had covered the conflict in Northern Ireland in 70s and 80s stated that they would not cover the conflict in the same manner if it took place now; another stopped writing about child abuse when they thought about what their search history may look to someone else; when they heard of a conviction based on the ownership of the Anarchist Cookbook, a participant who bought a copy for research shredded it. Further to this a participant stated: "I think I would avoid direct research on issues to do with Islamic fundamentalism. I might work on aspects of the theory, but not on interviewing people…in the past, I have interviewed people who would be called…'subversives'."

An earlier survey of US writers found that 1/6 reported self-censoring because of surveillance.