Microsoft (via @SwiftOnSecurity, comments):
Since we started to roll out unlimited cloud storage to Office 365 consumer subscribers, a small number of users backed up numerous PCs and stored entire movie collections and DVR recordings. In some instances, this exceeded 75 TB per user or 14,000 times the average. Instead of focusing on extreme backup scenarios, we want to remain focused on delivering high-value productivity and collaboration experiences that benefit the majority of OneDrive users.
[…]
We’re no longer planning to offer unlimited storage to Office 365 Home, Personal, or University subscribers.
[…]
Free OneDrive storage will decrease from 15 GB to 5 GB for all users, current and new. The 15 GB camera roll storage bonus will also be discontinued. These changes will start rolling out in early 2016.
The FAQ also makes it clear that Microsoft looks through the contents of a user’s OneDrive account. Not that anyone doubted that before.
OneDrive is now more expensive than iCloud for the smaller capacities. It’s probably not a good idea to count on unlimited anything sticking around. Will Amazon be next?
Update (2015-11-04): Brett Howse:
The paid 100 GB and 200 GB tiers are now gone, and have been replaced with a single 50 GB offering for $1.99 per month. So you get half the storage now for the same price. Previously the 100 GB plan was $2 per month and the 200 GB option was $4 per month. This seriously reduces the number of tiers, and you now go from free, to 50 GB, to 1 TB, with no other options anywhere else.
Update (2015-12-16): Joe Rossignol:
OneDrive users who sign up by January 31, 2016 will be able to keep their 15GB of free storage and 15GB camera roll bonus, even after Microsoft reduces its free storage tier to 5GB next year. OneDrive customers using more than 5GB of free storage will also receive a free Office 365 Personal subscription with 1TB storage for 12 months.