They are sometimes forbidden, but they occur all the same.  Work place romance always occurs, and perhaps surprisingly, often leads to marriage.  According to a recent San Antonio Express news article, more than 20% of office romances lead to marriage.  One wedding planner says 25% of his weddings started in the workplace.  The parties are not always employed by the same firm, but work helped them get together.  

But, the article reminds us, people need to be professional about the romance and not allow the romance from getting in the way of work.  Amen.  The best work policies in the world cannot prevent employees from becoming unprofessional.  Emloyees must do that themselves.