When the headhunter comes knocking... In today's free agent workplace, employees have few qualms about jumping ship when they get a better offer. And in a booming economy, desirable workers don't even have to seek new opportunities--headhunters come to them.As a result, employers are having to work harder to retain talented employees. Ignoring the problem can be costly--eventually the cost of hiring and training replacement workers will affect the bottom line. Read on to find out what smart companies do to keep their best workers from roaming.If you're wondering whether your company needs an employee retention plan, consider the potential costs of employee turnover. The price tag varies from position to position and firm to firm, but it's not unusual for total costs to run