Google has launched Google Public DNS as an alternative domain name service for any Internet user. Designed to replace the DNS services provided by ISPs or companies, Google says that its DNS will be faster and more secure than many other DNSs, and won't filter content.
TechCrunch has it's own version for the reasons Google entered the DNS business:
In 2008 OpenDNS was making $20,000/day in revenue when they were resolving just 7 billion daily queries.
Here’s how money is made – when users enter a URL that can’t resolve, the service puts up its own landing page with search results and advertisements. And companies are very willing to pay for DNS services like these to stop employees from hitting malware sites (they are simply blocked), or other sites (porn, Facebook, etc.).