2011 July 18, Google official blog announced Google bought the domain name g.co:
Google needs more shorter domain name to replace the current shorter service: goo.gl;
When you visit g.co, you can find the following text:
You’ve arrived at this page because you typed or linked to “g.co”, Google’s official URL shortcut just for Google websites.
Whenever you see a short “g.co” link, you can trust that it will always take you to a Google product or service.
We also have a public URL shortener at goo.gl. You can use this to shorten up URLs across the web.