In a post on the Android Forums (via Life Hacker), user Brian706 posted a screenshot of a conversation that he had with Google support. In that conversation, it was asked if rooting the phone or flashing the OS would void the phone’s warranty when purchased through Google. Assuming the rep is correct, the simple answer is no, your warranty would not be voided.
The rep goes on to state that Android does support rooting, although they can’t necessarily guarantee functionality of the device should it be changed in a non-official way, which we guess is totally understandable. However there is a slight catch and that is should you bring your device back for an exchange during the warranty period, users will be required to return the device to the latest stable version of Android, meaning that you can’t return it while it has been rooted/running a custom ROM, which once again seems is understandable and reasonable enough.