Coinbase CEO here - can confirm it was not us.

Checked with the team and we couldn't find any interaction matching that description. http://www.reddit.com/r/Bitcoin/comments/1wtbiu/how_i_stole_...

We work with a community of security researchers who help us test these sort of things https://coinbase.com/whitehat including quite a lot on race conditions. We use a variety of datastores for different parts of the app where they are best suited.