ECC RAM really needed?

We're thinking of building some new servers.  We bought some a while back that have ECC (error correcting) RAM, which is absurdly expensive compared to the same amount of non-ECC RAM.  Does anyone have any real-life data about the error rate of non-ECC RAM, and whether it matters or not?  In my long career, I've never once had a computer that corrupted memory, or at least I never knew if it did.  ECC sound like a good idea, but is it solving a non-problem?

Thanks,
Craig