Not just immoral/unethical jobs either - but sometimes other jobs which some classes of people consider "less desirable". It's the social network guys these days, but back in the late '90's I learnt more about large-scale highly-available and secure web development from people working in the porn industry than anywhere else. (I remember a long and fascinating/educational series of conversations with Sudicide Girls tech people at the Open Source Convention in San Diego back in 2000 or 2001.)