Bloat on Android phones comes in the way of pre-loaded applications, skins and UI, and now we have Rich Minder, the co-founder of the Android project and current General Partner at Google Ventures stating that he was surprised that carriers haven't spent more time and money making new and unique user interfaces for their devices.
Android is an open platform, giving both carriers and manufacturers the freedom to tweak and customize the Android OS how they see fit. Miner said at the Open Mobile Summit conference, "There's a big opportunity that they seem to have left on the table".
Most carriers have pre-loaded at least something onto an Android device, with pre-loaded apps or a custom UI from a manufacturer, but none of the carriers have produced their own custom skin. This leaves the work for the manufacturers to do, in order to differentiate their tablets and smartphones.