Twitter as a consumer megaphone: Fighting back against aggressive marketing by Comcast [BizJournals]

On average, people tell 24 others about a bad customer service
experience and 15 people about a positive one. According to the
American Express study, the effect is magnified on social media: After
a bad experience, dissatisfied consumers tell 53 people, and happy
consumers spread the word to 42 people.

http://www.bizjournals.com/seattle/blog/techflash/2012/10/twitter-as-a-consum...