While exchanging rants this week with Marcus Pradel, he brought up the idea of Online Quiet Mode. One of the reasons AT&T wants to restrict laptops tethering to iPhones and such is because they will agressively use bandwidth because they believe they have broadband connections.
A feature missing from laptop and netbook operating systems is the ability to dynamically turn off background updates and other things that will eat bandwidth and battery life. Truly mobile devices and most tablets ( tablets are portable but not really mobile aka in your pocket ) understand that you may not want to download attachments or other 'heavy' usage.
This feature would be primary triggered when the device goes onto battery power from wall power as least as an option and perhaps triggered more agressively if battery levels drop. In this mode, background applications or downloads would be signficantly throttled or restricted both in CPU and Internet access.
A programming heirarchy would allow multiple tiers of access or throttling based on types of connection. This could be manually set or automatically determined in the way that many p2p clients determine available uplink speeds. Ping times over mobile networks typically are higher to the next hop and contain high jitter.
The current problem is that most operating systems or devices assume the speed from the link connection. Just because you have a full speed 802.11n connection, does not mean you have 300Mbit of bandwidth past one hop.
Similar to how some programs like Norton 360 allow you to select which programs run at startup or delay startup, Online Quiet Mode would allow you to select or preference which applications can be used with bandwidth or power needs to be conserved.