Keyword Volume is vitally important to Internet Marketing. It may be the most important ingredient to SEO success, but finding accurate (believable) keyword volume is all but impossible.

Accuracy (un)Achievable

http://moz.com/community/q/accuracy-of-search-volume-for-keyword-planner-v-old-keyword-tool
http://lukeglassford.com/2013/11/28/search-volume-study-can-you-trust-googles-keyword-planner/
http://www.samapplegate.co.uk/keyword-research/how-accurate-are-the-keyword-tool-monthly-search-figures/
http://www.seochat.com/c/a/google-optimization-help/is-googles-keyword-tool-accurate-analysis-using-actual-data/