I run ZFS with ECC now, but for about 5 years I used it without ECC, and all else being equal, given the choice between ZFS without ECC, and forgoing ZFS altogether, I'd still go with ZFS. Memory errors can happen, but they seem to me to be relatively rare; I've no knowledge that I've ever suffered from one except when the DIMM was very definitely faulty (and ECC won't necessarily save you from that, though it will give early warning of the problem), and I don't think I've ever actually heard of someone's ZFS system being wiped out by one. (There appears to be a certain amount of folklore grown up around ZFS, perhaps as a result of people repeating recommendations without really knowing the justification for them, so I do appreciate it can be difficult to gauge these sort of concerns.)
On the other hand, disk electonics failures, disk controller failures, backplain failures, all do happen. Frequently. To me. (Well, more frequently than I'd like), and when they occur intermittently, these classes of failures will produce on-disk corruption, but that ZFS can withstand, even without ECC. So I would gladly take ZFS's protection against these, even at the risk of whatever it is that a memory error might produce.
Lastly, consider that if the data is important enough to warrant worrying about memory errors, it's important enough to have backups.
On the other hand, disk electonics failures, disk controller failures, backplain failures, all do happen. Frequently. To me. (Well, more frequently than I'd like), and when they occur intermittently, these classes of failures will produce on-disk corruption, but that ZFS can withstand, even without ECC. So I would gladly take ZFS's protection against these, even at the risk of whatever it is that a memory error might produce.
Lastly, consider that if the data is important enough to warrant worrying about memory errors, it's important enough to have backups.