I have never employed a private investigator, but if I never need it I will do it. I think most part of them make a good work.
The only experience I had with private investigators was when I was working as a director secretary in a big company and one employee lied the company about his ilness (he did not come work baecause he said he was ill but it was false and he had another job in black market). So the company decided to investigate him.
I would never have this job bacause I wolud be afraid. People use not to be very kind when they realise that someone is following them.
I have never had strange jobs, but when I worked as a director secretary in a big company I had to make many different works: pick up clients from the airport, contract stands for fairs on USA and all over Europe, send bottles of wine to clients for Christmas, to put in order the office of my boss (in order to find a cheque from a client), go to the administration for the export licences. Every day was different!