Based on Sprint's "Now Network" promotion, the company has launched a customizable screen saver that allows to access multiple services and types of content:

While screensavers are nothing new, Sprint has overhauled the familiar application in a fresh and exciting way to encapsulate the depth, breadth and power of the Sprint Now Network. The NOW customizable screensaver, which launched today, lets you see the present moment on your screen by drawing in information from your Facebook, Myspace, Twitter, YouTube and Flickr data. In addition, it enables you to tailor other real time elements, such as local traffic and bus schedules, the weather, and even how many Google results match your name!

Customization/personalization is one of the ways that carriers can remain relevant to end users as more subscribers opt for mobile devices that offer full browsers. The "carrier deck" becomes less and less relevant or entirely absent when users are on the iPhone or Android for example. There was a deck of sorts on WinMo 6.1. But people will increasingly just go to apps/widgets or directly to the Internet.

On the back end, with user location and other user data, carriers can potentially get a piece of ad revenues by providing some of that targeting data to third party publishers and ad networks (provided the FTC doesn't bar it). However as consumers migrate to more Internet-cable phones carriers will need to offer positive reasons to consumers to interact with their content. AT&T and Verizon have accordingly said they'll be creating apps stores. 

But I imagine a situation -- a more "robust" version of what Sprint is talking about -- where users can customize a start page with third party content. Some portion of that page could be reserved for carrier branding and messaging or carrier-sold ads. This is analogous to MyYahoo today. 

But for these more compelling tools and services to mobile subscribers, the "dumb-pipe" scenario looms larger and larger for operators.