Employment attorneys tell me that the reason retaliation claims are on the rise is that retaliation is much easier to prove than harassment. Some plaintiffs lawyers are even 'giving up' on a harassment complaint and just focus on retaliation as a result.
When I conduct workplace investigations, one of the things I look for is whether retaliation has taken place. It may be that there was no actual harassment - but there was retaliation.
The simplest example is when an employee is terminated shortly after making a harassment or discrimination claim. The burden is on the employer to prove he or she did not terminate because the accusations were made.
And retaliation can be much more subtle - co-workers avoiding the accuser; management moving the accuser to another office or work location.
Make sure you add a non-retaliation policy to your employee handbook. But you need to be vigilant in making sure the policy is truly in practice.
This excellent article from Shaw/Valenza illustrates some recent retaliation decisions made by the courts.