Microsoft and Dropbox have joined forces to make it easier to use productivity applications on mobile devices and on the Web. The partnership integrates the collaborative services of Dropbox and Microsoft Office so users can share and edit documents, spreadsheets, and other files. File-based services like Dropbox have been eyed with suspicion about security and concern by vendors worried it could chip away at their share of the market. Microsoft has been no exception, viewing Dropbox as a possible competitor to OneDrive, its own file-sharing application.