In Dotcom's typical grandiose style, the launch featured a tongue-in-cheek re-enactment of the dramatic raid on his home a year ago, when New Zealand police swooped down in helicopters onto the mansion grounds and arrested him in a safe room where he was hiding.
"Mega is going to be huge, and nothing will stop Mega - whoo!" Dotcom, 39, shouted from a giant stage in the grounds of his mansion, seconds before a helicopter roared overhead and faux police agents rappelled down the side of his mansion.
Kim Dotcom's house in Coatesville, north west of Auckland, New Zealand
Interest in the site has certainly been high, with Dotcom claiming half a million users registered for Mega in its first 14 hours.
US authorities are trying to extradite the German-born tycoon from New Zealand, where he is free on bail. Prosecutors say Dotcom made tens of millions of dollars while filmmakers and songwriters lost around $500 million in copyright revenue.
Dotcom argues that he cannot be held responsible for copyright infringement committed by others, and insists Megaupload complied with copyrights by removing links to pirated material when asked.
Mega, like Megaupload, allows users to store and share large files. It offers 50 gigabytes of free storage, much more than similar sites such as Dropbox and Google Drive, and features a drag-and-drop upload tool.
The key difference is an encryption and decryption feature for data transfers that Dotcom says will protect him from the legal drama that has entangled Megaupload and threatened to put him behind bars.
The decryption keys for uploaded files are held by the users, not Mega, which means the company cannot see what is in the files being shared. Dotcom argues that Mega - which bills itself as "the privacy company" - therefore cannot be held liable for content it cannot see.
US prosecutors declined to comment on the new site, referring only to a court document that cites several promises Dotcom made while seeking bail that he would not - and could not - start a Megaupload-style business until the criminal case was resolved.
Dotcom denied the new site was designed to provoke authorities, but got in plenty of digs at their expense, saying that their campaign to shutter Megaupload simply forced him to create a new and improved site.
"Sometimes good things come out of terrible events," Dotcom said. "For example, if it wasn't for a giant comet hitting earth, we would still be surrounded by angry dinosaurs - hungry, too. If it wasn't for that iceberg, we wouldn't have a great Titanic movie which makes me cry every time I see it. And if it wasn't for the raid, we wouldn't have Mega."
Kim Dotcom in court in Auckland following his arrest last year
The arrest last year was not Dotcom’s first brush with the law. Often labelled “Germany’s most notorious hacker”, in 1998 he was given a two-year suspended prison sentence for a string of hacking offences stretching back four years, including theft of trade secrets. He had penetrated security systems at banks and utility companies, and stolen tens of thousands of pounds.
Following his conviction, Dotcom set up Data Protect, a computer security company. He sold his 80 per cent stake in 2000 at the height of the dotcom boom and became a millionaire. The firm went bust in 2001