Word on the grapevine is saying that Google is doing similar. One of the "perk" of being a well-known DNS resolver (8.8.8.8) is getting an early notification whenever a server goes "online" on the internet.
Please elaborate.
For their computer to resolve this domain name, it's going to call out to a DNS server, of which Google hosts a major one. It can be assumed that they log these names, and can then use that as a "notification" for a site coming up.
So you need: IP address and port for the TCP headers, and the domain name to go in the TCP packet content.
One example of a vulnerability would be having phpMyAdmin with a database password hardcoded and no login needed. Without the domain name it would still be impossible to access. (Of course, domain names shouldn't be considered secret so this would be a very insecure setup.)