Based on a survey conducted by the entertainment research group, EEDAR, a great amount of gamers who do not buy downloadable content are those who wish to protect their privacy.
The survey was taken by roughly 3,500 people and 47% of them agreed privacy was a huge factor. 38% of them said they wouldn't buy DLC because of the 'no return policy' and then 32% said they wouldn't because DLC is just too expensive. Only 11% won't purchase them based on their quality.
With all that being said, the EEDAR estimated that DLC will bring in about $875 million by the end of the year and then nearly $1 billion in 2012.