Cloud storage services like Dropbox and Google Drive (disclosure: I work for Google), should simplify their quota system.
To begin with, deleted files should be available forever as long as you’re within quota, rather than for just 30 days. Put differently, you should be able to fully use the quota you paid for. Deleted files should be permanently deleted only when you run out of quota. Even then, only as few files as needed should be permanently deleted, to bring you back within quota.
Let’s say you have a 100GB quota, of which you’ve used 80GB, plus 20GB trash. The trashed files should be indefinitely available, assuming you don’t upload new files or edit any existing files, since you haven’t exceeded your quota. Now let’s say you upload 1GB. This should cause only 1GB of the 20GB trash to be permanently deleted (the oldest 1GB of files in the trash, naturally).
This goes for previous versions of files, too, which Dropbox saves for 30 days. They should be saved indefinitely as long as you’re within quota. And don’t charge users extra for this, as Dropbox does.
Duplicates shouldn’t be counted against your quota, since Dropbox dedupes them. It doesn’t cost them any more to store another copy. This simplifies scenarios like backup. You no longer have to do incremental backups. You can do a full backup every time, and Dropbox makes it an incremental backup behind the scenes, by deduping unchanged files, which are usually the majority. This is smart, but works only if you’re not charged again for the quota.
Users should also be charged only when they start using what they’re being charged for. As an example, Google Drive has a 15GB free tier, and 100GB and 1TB pair tiers. If you signed up for a paid tier, you should not be charged immediately. Instead, you should be charged only when you actually use more than 15GB of storage. If you never do, you’re never charged .
Similarly, if you opt for the 1GB plan but end up using only 100GB, you are charged only as per the 100GB plan. This effectively makes the plan a maximum limit on your spending, rather than a fixed amount.
Switching gears, Dropbox has only one paid tier — 1TB for $100 annually. I don’t need anything close to a terbyte of cloud storage, and $100 is a non-trivial amount of money, so Dropbox should have a $50 tier (half of $100), and a $25 tier (again, half of $50). They can be proportionally smaller, or even more so. That is, if I get a terabyte for $100, I’d ideally get 512GB for $50. But I’d be perfectly happy with 256GB as well — that’s far more than what I need. What matters is that I’m saving $50.
In other words, Dropbox is still too expensive, at $100, for the space I need, which is a few tens of GB.
Finally, Dropbox offers both a $10 per month plan, and a $100 per year plan. The yearly plans have a discount — you don’t end up paying $120. That’s fine, but if someone decides mid-year that they want to stop using Dropbox (or switch to the free tier), they should be given a refund for the remaining amount after being charged for the months they actually used Dropbox, at the monthly rate. For example, if after six months, you decide to discontinue paid service, you should be be charged 6 * $10, which is $60, and get a refund of $40. Note that I’m not asking for a refund of $50 on the logic that you used the service for half the duration you paid for (1 year). I’m happy with $40, but Dropbox doesn’t give any refund, effectively locking you in. This should change.
In summary, there’s a lot of room for improvement for quotas on cloud storage services, to make them even more user-friendly.
 Alternatively, bill me immediately based on the plan I use, but if I end up using a lower tier of quota during the entire billing cycle, then give me a credit based on the difference between the tier I paid for and the one I actually ended up using.
 And, even after you start being charged, if your usage drops below 15GB throughout a particular billing cycle, then you should stop being charged until you again exceed the free quota.