Absolutely. I think code reviews make sense for knowledge sharing and improving the quality of the code. Most people during code reviews don't actually find bugs in their comments, according to some research done by Microsoft.
http://research.microsoft.com/pubs/180283/ICSE%202013-codere...
The Quora post specifically says they review code after it is live in production:
At Quora, we generally do post-commit code reviews. That is, the code goes out live in production first and someone comes and reviews the code later.
I'm highly skeptical of code reviews as the way to find bugs. I think code reviews have other values, just not that one so much. Getting multiple eyes on code and the results of that code, getting it into the hands of QA, dog fooding it, all play a role. That all sounds way more ad-hoc than I mean it. I used to write life critical software, and you have well defined ways to handling source control and reviews. I advocate figuring out what your project needs, adopting that, and then continually adapting as the project changes, as any project will.