If you read the comments to the referenced article, someone had a rowhammer problem even with ECC memory. ECC does indeed reduce the chance of a memory error a lot, but the chance is far from zero (at scale of hundreds/thousands of servers), even with ECC. Another paradox about ECC, it's not a guarantee, so you still need to build systems that can tolerate / mitigate statistically rare memory error states.

This commenter seemed quite credible to me, here's where it starts:

http://discourse.codinghorror.com/t/to-ecc-or-not-to-ecc/377...

> Yep, these are what we had -- uncorrectable errors with ECC memory caused by row hammer. Luckily there are mitigations. Sandy Bridge allows you to double...