According to some people, changing your documents and files without telling you or asking your permission. That's true as far it goes, but it's not the whole story., the business cloud storage service formerly known as SkyDrive Pro, is
If you'd been paying close attention to OneDrive for Business, you'd already know that it's not simply an upgrade of the personal storage cloud service OneDrive. Instead, OneDrive for Business has long been based on SharePoint Workplace, where metadata is added as a matter of course to make your files more useful.
Officially, Microsoft explained, "Limited metadata is added to content to support advanced document management scenarios and preserve user experiences. Examples of this include synchronizing document properties across its parent folder to enrich discovery or updating links when a link has changed. The functionality behind this has been in the product for several releases and is designed to synchronize important metadata between a document and a Document Library including OneDrive for Business."
In short, Microsoft is not doing anything new. Nor is there any reason to believe that they've been hiding this information or using it to tag your files for their own purposes.
True, if you were using OneDrive for Business as if it were just a pure file storage service such as Dropbox, Microsoft seeminglt changing your files by adding metadata could be annoying or even upsetting. If you know what's really happening behind the OneDrive for Business scenes, the "changes" in your files make perfect sense.
That said, this episode does point out that whenever you're using any cloud service you do need to make sure you know exactly what your vendor is doing with your data. If you don't, finding unexpected metadata-driven changes to your documents could easily prove to be the least of your worries.