A false accusation of sexual harassment is a concocted story about one or more accounts of unwanted sexual remarks and/or frequent attempts to initiate a sexual relationship. Accusations of this nature can occur within the general community, the workforce and the education system.
In the workforce and education system, sexual harassment includes rude and/or sexist jokes that are stated by a man while he is within hearing distance of a female colleague.
Most accusations are filed by female employees and female students.
The two main incentives are financial gain and spite, respectively, though the latter option has been used by angry employees who wanted to ruin a rival man's reputation. Attention seeking can be a factor, too.
Large corporations have been targeted by opportunistic women. Any claim, regardless of how absurd, can take a long time to disprove. The negative pulicity associated with a long, drawn-out court case can have a negative impact on the company's standing in the community. For example, a consumer might avoid dealing with the company until all doubt over their guilt has been determined. Not all members of the public accept a court's ruling when a company is cleared of wrongdoing, either. Due to this, quite a few companies have settled out of court because it was less costly than clearing their name. This is the reason opportunistic women have used this ploy.
There have been cases of students filing false accusations against their lecturers for rejecting their sexual advances. One case in particular, Peter Gauci v Cristelle Kennedy, exemplifies the severity of the issue.  According to the victim, Mr Gauci, he was falsely accused by Ms Kennedy after he cancelled a date at the movies -- he reluctantly accepted the request earlier, though only because he turned down her request to get a tattoo together. 
Here is an excerpt from the e-mail containing Gauci's cancellation of the movie date:
"I don't feel good about seeing a movie with you … For me it's unusual for a student to throw this at me [asking him to be friends] and the whole situation is just uncomfortable … You're probably a nice person, but we can't be friends. Please don't persist with this." 
Ms Kennedy responded with a threat:
"I'm not asking a lot of you. If I wanted to 'jump you' I would have done it a lot sooner than this … As for persisting, well I'm not one to go down without a fight. If I wanted to make your life hell I could." 
Gauci was subjected to questionable treatment by the University of Queensland and Anti-Discrimination Commission Queensland during the ordeal. His supervisor at UQ, Judy Bowey, refused to accept he was harassed, even though he provided evidence to show she was the aggressor. Bowey told him to apologise to Ms Kennedy. 
Peter Gauci revealed the following to MRO:
He responded to Kennedy's threat by reiterating he would not date her. She filed the allegation at this point.
His employer, University of Queensland, found him partly guilty of the allegation brought against him. In his words, UQ's evidence consisted of nothing more than a "non-existent confession". He says Kennedy confessed to lying after she found out he is homosexual, but UQ ignored it.
Cristelle Kennedy created a fake e-mail account under his name, then sent fake death and rape threats to her e-mail. She used the fake death and rape threats to convince a magistrate to accept her request for a Peace and Good Behaviour Order against Peter. He says the police have ironclad evidence she faked the e-mails, and, as a result of said evidence, were able to obtain a confession from her: the account, which was made on Hotmail, was frozen and preserved after Peter informed them of the situation, then the police traced the IP address of the e-mail account to Cristelle Kennedy.
Apparently, Ms Kennedy has pulled the same stunt on other people. 
Marriner, Cosmima. Uni tutor who turned down date wins right to appeal over spurned student. Sydney Morning Herald (30 July 2007) [Webpage]
Gauci, Peter. Lies, sexual harassment, and I wish I'd had a videotape. Independent Media Center (15 January 2009). [Webpage]