Looks like Verizon Wireless has taken a page out of AT&T's playbook, as the latest Gingerbread update for the Droid X now seems to detect tethering apps not approved by the carrier and cut off users' data, replacing all requests with an upsale page for the official hotspot add-on. This is now the 2nd wave of attacks against free tethering, following a global carrier block (with the exception of good old Sprint) of the most popular tethering apps on the Android Market.
According to a Reddit community member with a melodic name Poop_Cooper, all data on his Droid X was suddenly cut off after he updated his Droid X to the latest Androd release and started using the popular Wireless Tether application to share his mobile connection with devices around him. 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. Only a reboot ended up fixing the problem, although one of the commenters suggested an airplane mode toggle as a faster revival technique.
Whether you agree with the technique or not, Verizon seems to be operating within the terms of its wireless agreement which prohibits unauthorized use of tethering:
Customers who do not have dedicated Mobile Broadband devices cannot tether other devices to laptops or personal computers for use as wireless modems unless they subscribe to Mobile Broadband Connect.
At this point, it's not immediately obvious whether such detection happens on the device itself or on the VZW network level, but all signs point to the former. If so, Android modders should have no problem coming up with a solution, neutering such detection at its root. For the latter case, even easier solutions, such as rewriting all user-agent request headers, already exist, so while either technique will likely stop an average user, the persistent ones among you will always be able to get what they want.
If you've experienced the situation described here, feel free to share your experiences and possible solutions down below; otherwise be warned - Big Red is watching you.