Yep - but can provide the same (or better) error recovery by just keeping systems and software redundant. So while ECC RAM makes sense by itself, it is by no means a non-substitutable necessity.
Errrr, no. This is the same spin that was offered up when VaTech tried whipping together a supercomputer with non-ECC G5s. "We'll just do the computations twice and compare". When ECC macs arrived they ripped those non-ECC models as quickly as possible.
ECC is useful not only in correcting errors but also in informing you that you had one. Non ECC systems won't tell you anything.
If you data isn't valuable then you don't need ECC. If you data is valuable you can benefit from it. A single pixel in a video stream has a miniscule value so that's which video cards don't care. There are lots of errors in the data, but that data only have value in expensive bulk. (and frankly even in bulk some isn't valuable either. )
Nobody buys storage drives without ECC. The drives could all be very incrementally cheaper if keeping the data in intact is made a non issue. Practically, nobody thinks data rot on there disks is a good thing.
Once get into the double digits GB of RAM, ECC has benefits.
In current forms ECC is not that significantly more expensive. The only "boost" can get is that often faster memory ( if going to be overclocking) or denser memory ( if going to insert larger DIMMs than on Apple's specs ) is an issue.
Redundant components and failover software are useful and effective for whole component failures. Not single bit errors.