[deepu_256]

Well, may not exactly big but Quora is using Tornado in production.

[tzury]

Yes, but not the whole Quora anymore, Right now, they use it just for pushing chunks of javascript to browsers

[1] http://www.quora.com/Has-Quora-made-any-modifications-to-Tor...

[2] http://www.quora.com/How-does-Quora-use-Tornado