OneDrive has a base storage limit of 15GB for a free account. Microsoft, in promotion of a setting to automatically upload photos to their storage service, is offering an extra 15GB if you enable this feature before the end of the month. That is 30 total GBs! As of their September 10th blog post, they will also allow files of up to 10GB (!!) in size. That is a pretty big picture or movie.
Through this initiative, Microsoft hopes that more people will sign up for OneDrive and those with accounts will integrate it into their lives. Large storage capacities, mobile apps, applications for Windows and OSX, large file support, and affordable storage tiers definitely make a compelling platform, one that puts pressure on Google and Dropbox.
The question is whether you trust Microsoft with every photo or video that comes off of any given device. While some could find it compelling to have up to 30GB of extra storage for their cameraphone, without the need to manually sync, I could see others who want to be more selective.
You can enter this promotion before "the end of the month" (which is a little vague).