A few months ago AT&T, T-Mobile, and Verizon all started blocking wireless tethering apps in the Android Market, making them unavailable for download on their respective devices. At that time, Sprint was the only carrier still allowing tethering apps to be installed without limitation -- but that time has come to an end. That's right, the Now Network has begun blocking the installation of wireless tethering apps from the Market on any device attached to its network.
While this is disheartening indeed, there is always a workaround. Sprint may be able to block specific apps in the Android Market, but it can't stop you from pulling an app directly from the web and sideloading it onto your device.