Why on Earth Would You Want to Conduct an Online Investigation on a Perspective Tenant or Employee?

Why conduct a background check? If you are an employer or a landlord and you have just received an application or conducted an interview with a person, that up to a short while ago you really knew absolutely nothing whatsoever about, for a position in your employ or to rent and live in your apartment, then you have every right to immediately carry out a background check on this person's past history.
Taking this precaution, you may discover events that may have been omitted on the person's application form and resume. Armed with this knowledge obtained from a background check, you will be better able to make an informed decision as to whether or not you hire the person concerned or allow them to rent your accommodation. Been there done that.
I have myself conducted interviews with certain people who have thoroughly impressed me with some of the answers to my questions.

However on performing a background check following the interview I realized I couldn't have been more wrong in my assumption and I had been entirely misled. In today's day and age, because of the increasing risks in the society we live in, we just can't afford to offer people the job opportunity or an apartment without doing some kind of a background check to make sure that whether these people are who they claim to be and have a trustworthy background.
Why would a person lie in the first place? It stands to reason, that many people who have committed criminal offenses and therefore have earned themselves a criminal record, balk at the idea of admitting to some arrest record that could jeopardize their application.

They would never voluntarily reveal anything that might harm their applications or resumes.

By performing a background check, details such as a record of criminal activity, that have been omitted are more than likely to surface.
There's an old saying, 'The truth will out', how very true.
A Background Check can also apply to a Company.
It is not only a prospective employer that a background screening through the public records might benefit.

These searches may also be carried out by the employee. Company record searches are also carried out by many employees in order to know something about the company and the employer before they even apply for the position.
An underhanded company for instance with maybe a larger than usual turnover of staff, is not one that an honest person looking for an honest days labor would care to apply too in the first place.