Kim Dotcom’s comeback file sharing service, Mega, has been designed to shield Mega from allegations of knowingly hosting and profiting from rampant piracy. Everything you upload is encrypted before it leaves your browser, using a key that is only ever known to you. Mega is driven by JavaScript (not Java!) inside your browser. Critics have already taken issue with some aspects of Megas implementation, notably including the. terms of service explicitly state that the service may automatically delete a piece of data you upload or give someone else access to where it determines that that data is an exact duplicate of original data already on our service”]
Source: https://nakedsecurity.sophos.com/2013/01/23/crypto-critics-take-on-kim-dotcom-and-mega6/