Some employers are inevitably concerned that a virtual assistant will charge for hours when they are actually watching television. Silicon Valley’s oDesk, for example, provides some assurances. When an assistant is logged into a job on their computer, an automated program takes six snapshots of the screen every hour. The employer can check those images remotely to see whether their assistant is fooling around on Facebook (FB).
SOURCE LINK to full article: http://www.businessweek.com/articles/2012-09-04/when-your-personal-assistant-is-virtual