It's certainly possible to run zookeeper across multiple datacenters at scale as yelp has demonstrated, however we've elected to make a different set of tradeof

It's certainly possible to run zookeeper across multiple datacenters at scale as yelp has demonstrated, however we've elected to make a different set of tradeoffs. Our goals include reducing operational complexity and being able to minimize the impact of node failures, i.e. quickly remove them from consideration by clients.