Good for privacy litigation. "My client had DNT in her browser set to 'on' and the company intentionally ignored this and tracked her actions on the web, vioalting her right to privacy and causing monetary damages in the amount of $________."

Web developers might hate it, but DNT could be potentially good for end-users who want to make privacy claims. It's just one extra header. A few extra bytes. Meanwhile things like XML and JSON, which add considerable bloat to web responses, are accepted without any complaint.

On the other hand now every single line of code that gets changed has to reviews by a lawyer to make sure it is compliant with the DNT legislation. And if your a startup, the best way to take you down is probably a couple of frivolous DNT lawsuits.

CSV is beautiful - for numbers. When you invoke strings, and quoting, and whatnot, it goes downhill fast. :)

But you need a lot of extra RAM compared to the usual filesystems. Is that correct? If yes, is using ZFS worth the cost of the extra RAM?

You don't need the extra ram. ZFS uses it as a cache, more ram, more cache. That's about it, otherwise it doesn't use much ram.

ZFS doesn't use that much RAM if you don't turn on deduplication, which is of less use in a system that serves large compressed video files than one that handles tons of read/write traffic as an office file server.

RAM is not required; it just makes lookup faster with caching.