There has been some controversy over the features being added to the Dash to allow online searching, such as searching Amazon and Google Docs, etc. in Ubuntu 12.10 Quantal Quetzal. But it is easy to manage.
If you work in a corporate environment or just want to retain privacy then you just need to modify the privacy features in the System Settings as follows:
Go to the top right of your screen and click on the System Menu and select System Settings.
In the System Settings window click on Privacy:
Then switch the online search from ON: