Mr Justice McCloskey made the award against an unidentified defendant who hid behind pseudonyms during an online campaign of vilification lasting months.
Even though those responsible for posting the comments and images remain unknown, the financial penalty will be enforced should they ever be identified.
The judge also warned of the consequences for increasing abuse of social media.
Writs were issued by the company, the directors and employee last year after a series of messages and information about them was posted on Facebook.
The firm was granted anonymity on the basis that any disclosure would only draw more unwanted public attention.
Although the case against Facebook Ireland Ltd was dismissed, proceedings continued against a second defendant known only by two pseudonyms.
Barrister Peter Girvan, appearing for the plaintiffs, argued that damages should be awarded to compensate for the malicious lies.
He told the court his client is a well-known company.
With no appearance by the defendant, Mr Justice McCloskey held that defamation had been committed.
"They are, of course, hiding, behind a mask," the judge said. "However, as this case demonstrates on procedural issues our legal system in the modern era adopts a robust and realistic approach.
"As a result the defendant's attempts at concealment and harassment have been thwarted."
He found that libellous postings on Facebook specifically identified at least two of the plaintiffs, while other comments identified them by reference and implication.
Although the comments were held to have been widely read, debated and discussed, the judge decided publication would have been more widespread in a major newspaper.
Mr Justice McCloskey also took into account the length of time the defamatory material appeared.
He awarded £20,000 damages to the plaintiff who suffered the most distress and anxiety. The two others were awarded £10,000 and £5,000.
The defendant must also pay legal costs if they are ever identified.