Meteor is an awesome way to build realtime single page apps. It is still in preview stage but it is not a toy tools anymore and people want to build real apps. See Telescope one of the awesome app build with Meteor.
Once people started to build large scale apps, there is a common issue everyone is facing.
How to scale my app?
Unfortunately Meteor has no official (or builtin) way to scale. Don't worry there is solution for that, it is Meteor Cluster
Meteor Cluster is a smart package which allows you to sync Meteor Collections across set on Meteor node. Checkout my article on Meteor Cluster and How It Works for setting it up.
Once you have few Meteor nodes with Meteor Cluster, you need a way to load balance connections between them. Setting up load balancing for Meteor is tricky. Simplest solution is to use a cloud provider for hosting your Meteor Apps. Try nodejitsu or modules, they will take care of the load balancing for you.
UPDATE: Checkout my article on load balancing for Meteor