A little more than a year ago, Megaupload was taken offline by the United States government due to copyright violations and piracy. Many users lost their data that they stored on Megaupload, whether the data was legit or pirated. Kim Dotcom didn't like this decision, and decided to make a successor to Megaupload, dubbed Mega.
Mega has shown off images of the website before, and so far adoption has been positive. Kim himself said that bandwidth grew from 0 to 10 TB in the first few minutes. They had hundreds upon thousands registering every minute.
Mega will be different from the ground up, especially in security. All data stored on Mega will be encrypted and additional recordings such as how fast you type and how your pointer moves across the screen will be used to make sure that a person accessing your files is really you. You can also share files with other users, via a encryption key. Mega wants you to keep these keys private, so they created a messenger service that allows you to share encryption keys securely as well.
If you do want to share something, you can also include the encryption key in the URL, so users won't have to do a thing but click on a link.
For now Mega uses Google Chrome to power the website, and they detailed reasons right here in this blog post. Basically they say that Chrome meets all of the technologies to make Mega do its best, and other browsers are either lacking something or just don't have the required features at all.
As of the time of this posting, Mega has over a million users, and the user count is growing fast. If anyone wishes me to take a deeper look into this just let me know :).