Are there any statistics or estimates on the ratio of Tails users vs. Tor Browser Bundle users?
Following metrics have been released by Tails team.
In June 2014:
Tails has been started more than 331 862 times in June. This makes 11 062 boots a day in average. 25 124 downloads of the OpenPGP signature of Tails ISO from our website. 71 bug reports were received through WhisperBack.
In July 2014:
Tails has been started more than 355 608 times in July. This makes 11 471 boots a day in average. 35 134 downloads of the OpenPGP signature of Tails ISO from our website. 160 bug reports were received through WhisperBack. We discovered in late July than one of our WhisperBack relay was not sending emails anymore since our fixes of the Heartbleed bug. This explains the bump in the number of bug reports.
Based on the assumption that Tor has been started between 2000000 to 2500000 times per day, the ratio of Tails to Tor start in round numbers is in the range of 1% to 2%. However, each individual may start Tor or Tails several times per day, thus the number of Tor and Tails users are less than these figures. Finally, these figures do not provide an accurate estimate of Tails user to Tor users since one can not assume that Tails user have on average same behavior as Tor users. One would think that an average Tails user maybe more concerned about their anonymity than an average Tor user. By the same token, on average Tails users maybe under more surveillance than Tor users by global adversaries.