title_body: What are risks and disadvantages of publishing DRM-protected books for an author? What are risks and disadvantages of publishing DRM-protected books for an author?
  
  Clearly some authors think that there are disadvantages of using DRM since they publish books without (e.g. Eric Flint).
  
  Please note that I'm looking for hard data, not opinions. 
  
  "DRM reduces sales" is an opinion. "Switching from DRM to non-DRM raised sales by 30% for author XYZ" is a fact. 
  
  "People prefer to buy non-DRM books" is an opinion. "Sell-through, or buys-per-click from publishers with DRM for the same book is 20% less" is a fact. "A survey of XYZ large sample of users confirmed that 50% won't buy DRM-protected books" is a fact.
upvoted_answer: Self-published authors (who are going to be the only authors with the opportunity to decide on DRM vs DRM-free) will need a support mechanism for handling DRM-related problems. After all, any distraction from writing limits your income (see the famous clam sundae digression, p.25  in RA Heinlein's The Cat Who Walked Through Walls for an example.)