I was on the free plan (which I'd worked up to 10.5GB of storage through various incentive programs they ran) and specifically objected to

1. Limiting me to three clients at once. (Work computer, personal computer (Linux), personal computer (Windows), phone—oops!

2. Bombarding me with "your storage is almost full!" notifications either by email or when I visited dropbox.com to, e.g., get a share link for someone. Usually I had over a gigabyte of storage left. The webapp was at times unusable due to the volume of notifications.

3. Prohibiting me from keeping offline copies of entire directories on my phone.

Now I'm spending $20/month on a VPS running Nextcloud and am much happier.