(Reuters) -Activist investor Elliott Management owns a large stake in Dropbox and has been holding private discussions with the file-sharing service provider for some time, a source familiar with the matter said on Wednesday. The hedge fund owns a stake of more than 10% which is valued at more than $800 million, the person said, declining to reveal the exact size of the investment. Dropbox, which was co-founded by Drew Houston who is currently the company's chief executive officer, is valued at roughly $11 billion.