When you absolutely have to have it. Black Markets.
http://www.theguardian.com/world/2012/may/27/kidney-trade-illegal-operations-who
http://www.backgroundcheck.org/9-most-coveted-items-on-the-black-market/
http://www.statisticbrain.com/black-market-illicit-trade-statistics/
http://nakedsecurity.sophos.com/2012/12/06/tor-deepnet-anonymity/
http://money.cnn.com/2013/10/02/technology/silk-road-shut-down/index.html
http://www.wired.co.uk/news/archive/2013-10/09/silk-road-guide
http://www.cracked.com/article_19658_5-things-you-wont-believe-spawned-black-markets.html
http://www.thesmokingjacket.com/humor/seven-insane-black-markets-you-wont-believe-actually-exist
http://nymag.com/news/features/tide-detergent-drugs-2013-1/
http://www.havocscope.com/black-market-prices/endangered-animals/
http://gizmodo.com/5904129/heres-how-much-body-parts-cost-on-the-black-market
http://www.swide.com/art-culture/current-affairs/selling-your-body-how-much-are-your-organs-worth-on-the-black-market/2
