See this link for removal: http://www.thesafemac.com/art/
When installing apps you get from places like CNET & Softronics they wrap the installer with their adware. You have to manually uncheck NOT to install. I've seen the Genieo as "Install Genieo with a checkbox" in a very small font. See example here:
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OS X 10.9.3 added Genieo to list of incompatible software. If possible I would upgrade to Mavericks.