Ask HN: How feasible is it to encrypt user records?

With all the news around user data theft on an enormous scale recently, I wonder how feasible it would be to encrypt entire user records in storage. I imagine some data stores (e.g., key/value) would be more suitable for this than others. Are there any commercial/FOSS products that encrypt all identifying user data? Has anyone on HN tried implementing something like this? Is there a good reason (aside from obvious programming complexity and performance impact) that it's not a standard practice?