You don't always get what you want. The same can be said about work, you don't always get to do the work you love.
When all that office routine, colleagues, targets, and the boss suck big time, you start looking for something interesting in the monotony. For spicing things up, you start a relationship with either your colleague or your customer. With colleagues, it's kind of okay but fooling around with customers can cost you your job.
Here are some of the confessions from people who slept with their customers.