Supposedly, a Droid X user in the Reddit online community recently had his "unapproved" tethering detected and cut-off by VZW. Recently he updated his phone to Gingerbread, and tried to use the popular "Wireless Tether" app to share his mobile connection with his other devices. His connection was suddenly stopped and he was redirected to a Verizon up-sell page. Here's a quote from the AndroidPolice article,
It isn't immediately apparent whether the detection occurred at the hardware level or the network level. Are there any users out there that have or haven't experienced the same thing under the same conditions? Let us know in the thread.All outbound requests were suddenly redirected to an upsale page prompting to purchase a $20 add-on officially authorizing tethering to the tune of measly 2GB a month.
Source: AndroidPolice