1. Slight inconvenience 2. Strong inconvenience 3. Giving away "content" for free
I propose 4.: No inconvenience for the users, charge as you wish and simply sue the people making money illegally off your works.
Because the argument that it doesn't stop illegal copying anyway is correct. Consumers don't like it: http://www.amazon.com/Assassins-Creed-2-Pc/product-reviews/B... http://www.amazon.com/Spore-Mac/product-reviews/B000FKBCX4/ Those people giving 1 star reviews, those are the people who are interested in the game, research it, many of them probably pay money for it and then they are dissatisfied.
For text articles I think the big problem is really if someone copies an article and has some kind of decent traffic on the copy. This should be trivial to find via a search engine and you can take appropriate action directly.
For music and videos... I am not a friend of watermarks but it may be the best method of just selling drm free and going after those people who share the most "commercially".