From meterpreter.org
Why do you use Tor?
Protect their privacy from unscrupulous marketers and identity thieves.
Internet Service Providers (ISPs) sell your Internet browsing records to marketers or anyone else willing to pay for it. ISPs typically say that they anonymize the data by not providing personally identifiable information, but this has proven incorrect. A full record of every site you visit, the text of every search you perform, and potentially userid and even password information can still be part of this data. In addition to your ISP, the websites (and search engines) you visit have their own logs, containing the same or more information.
Protect their communications from irresponsible corporations.
All over the Internet, Tor is being recommended to people newly concerned about their privacy in the face of increasing breaches and betrayals of private data. From lost backup tapes to giving away the data to researchers, your data is often not well protected by those you are supposed to trust to keep it safe.