Why does Heroku warn against "naked" domain names?

view full story

http://serverfault.com – I ran across this page in the Heroku docs... Naked domains, also called bare or apex domains, are configured in DNS via A-records and have serious availability implications when used in highly available environments such as massive on-premise datacenters, cloud infrastructure services, and platforms like Heroku. For maximum scalability and resiliency applications should avoid naked domains and instead rely solely on subdomain-based hostnames. Does anyone here speak Enterprise? What are the "availability implications" they're warning about? (I notice that http://stackoverflow.com wo (HowTos)