Dropbox never took away anything they gave for free though. In the beginning they handed out extra space like candies, and the accounts that got it at the time still have it.
I dropped Dropbox with extreme prejudice (was a paying customer) when they decided to dictate which Linux filesystems I may use. Will never use them ever again. Randomly demanding I drop everything and re-engineer my stack is an invitation for me to re-engineer them out of my life.
Like everyone else, they have to decide what they support – their core product pretty heavily depends on known file system semantics – and they gave advanced notice specifically so you didn’t have to “drop everything” if you for some reason cannot have a partition using a supported file system.
Put another way, do you think the combined users of file systems which aren’t supported ext4, xfs, btrfs, or zfs are willing to pay more or would quietly accept the possibility of data loss? I doubt the former is true and have absolute certainty that if there was a bug using an unsupported file system that would result in angry, hyperbolic blog posts saying Dropbox is unsafe and will lose your data.
Oh are those all supported now? They've clearly backtracked massively. When I bounced they were insisting on ext4 only. Glad I didn't bother rebuild all my machines to ext4 only for them to change their damn minds. They gave us less than three months notice. I'm not playing chicken for three months paying their professional tier in the hopes they change their mind. Freaking circus.
The framing is not odd at all. Your framing makes it sound as if this was some requirement that had been known since the beginning rather than the typical "Good news! For our own corporate reasons we have decided to make your life better by jumping to the top of your todo list and breaking your things!" Thanks, I hate it.
To be clear it is trivial to thwart the check, but shared library shims can't fix the real problem which is pointless corporate contempt. Particularly if I'm paying for it.
They took away my "free" <huge amount of space for 2011> many years back. I mainly got the space hosting events at my university and other free work I performed for the company around that time as well as many, many referrals.
