webrtc.io.js was actually a symlink, and npm and nodejitsu don't package and deploy those (https://github.com/nodejitsu/jitsu/issues/379).
$ ls -al example/public
webrtc.io.js -> ../../node_modules/webrtc.io-client/lib/webrtc.io.js
So for now I put a workaround as a predeploy/postdeploy hack that copies the actually file into example/public/ from node_modules to be sent to the nodejitsu servers, and then revert it back to a symlink for local dev. There's probably a more elegant solution.
package.json: https://github.com/dougnukem/webrtc.io-demo/commit/3b1073d5b6af78100dd7e018f4a67b078ca552e6
"scripts": {
"predeploy": "cd ./example/public && rm webrtc.io.js && cp ../../node_modules/webrtc.io-client/lib/webrtc.io.js webrtc.io.js",
"postdeploy": "cd ./example/public && rm webrtc.io.js && ln -s ../../node_modules/webrtc.io-client/lib/webrtc.io.js webrtc.io.js",
"start": "node example/server.js"
}