OneDrive (previously SkyDrive and Windows Live Folders) is a cloud file service run by Microsoft, in both consumer and business versions, with various manners of accessing, modifying, and syncing the files supported, including Microsoft Office integration. It's been reported that Microsoft does all sorts of monitoring of user content (including by automated processes) to enforce various terms of service (it's apparently against their terms of service to have among your private files anything with partial nudity or discussion of purchasing firearms, or copyright and confidential files of course), banning people's accounts (even paid ones) and deleting people's files for alleged violations. It's also reported that the content of files gets modified automatically without notice, such as to insert odd Microsoftisms into HTML documents and added metadata to Microsoft-format documents (Word, Publisher, etc.), some of which might permit tracing which users created or accessed a file.
OneDrive produces many log files. See A parser for OneDrive .odl files.
Files stored in OneDrive are ephemeral. OneDrive users who do not sign in to their accounts or who do not do something with their files for two years will have a one-month notice sent to their email address; after which, if account reactivation was not done in that one month period, all of their files will be deleted.