But a growing number of Hongkongers are hiring them to check on the man or woman of their dreams to see if they measure up.
Hong Kong private eye agency Wilsons Global Investigation and Security Consultancy held the city's first detective seminar yesterday.
About 50 aspiring 'gumshoes' turned up in the hope of grabbing one of 30 new posts with the growing company.
In a video shown at the seminar, the firm showed how its services could be used to help people get to know more about the background and personality of the person they secretly admire before deciding whether to start a relationship.
'In this way, they can pursue the one they love more easily,' said Catrina Kwok Hoi-ching, administrative executive of the agency.
Global says its investigators help people learn the facts before taking the next step forward.
And the agency believes women make the best snoopers because they are more careful and observant and don't raise as much suspicion as their male counterparts.
For this reason, 95 per cent of their operatives are female. But yesterday the Wilsons Detective agency was out to find more male recruits.
Philic Man Hin-nam, the agency's investigation director, said: 'If the target goes to places like saunas or nightclubs ... male staff can ensure the safety of female staff.
'And in places dominated by men like mahjong parlours, we need to find male staff to fill the positions.'
Safety is a big concern and Kwok said: 'A team will be dispatched to do the job. The one who is doing undercover must be experienced.
'Assessments will be made on their emotional and psychological condition to be certain that the person can handle the job.'
She added: 'There is also training to teach staff how to deal with crisis situations, and some staff are sent to learn self-defence techniques. But so far, none of our investigators has been required to employ them.'
Another area that's proving big business for the agency is misbehaving children, for instance cases where parents suspect their children are using drugs.
Man said: 'I would describe us as actors, but unlike those on TV who can do a second take ... we need to be well equipped [through training] to deal with emergency situations.'
A new investigator works five to six days a week and the number of working hours is six to eight per day. The starting salary is between HK$10,000 and HK$12,000 a month. Kwok said the qualities they most need are logic and patience.