"There’s nothing special about ZFS that requires/encourages the use of ECC RAM more so than any other filesystem." -Matthew Ahrens (Cofounder of ZFS at Sun Microsystems and current ZFS developer at Delphix)
I think comes from an assumption that if you use ZFS you care more than users of other filesystems about getting the same data you have put onto disk out of the disk later when reading it back.
If that's important it's good advice to use ECC RAM. The point that's often lost is that if you cared about correct data, then having ECC RAM would have been a good idea regardless of using ZFS or not, and you're not worse off with ZFS than you would have been with another filesystem without ECC RAM.
Another common myth is that ZFS requires large amounts of RAM. It doesn't do that either, but the assumption is that if you use ZFS you're building some large multi-user system which benefits from a large cache. If that's not your use-case then that's not true, you could run ZFS on your single disk laptop if you wanted to.
"There’s nothing special about ZFS that requires/encourages the use of ECC RAM more so than any other filesystem." -Matthew Ahrens (Cofounder of ZFS at Sun Microsystems and current ZFS developer at Delphix)