[geoffschmidt]

Yes, if you're using DDP over sockjs instead of just over websockets (which Meteor currently does out of the box to support older browsers), you'll need to use a HTTP proxy with sticky session support.

This will be in the official docs at some point, but for now, Arunoda's blog post about this is a great starting point:

http://meteorhacks.com/load-balancing-your-meteor-app.html