Sorry if this is "old news",
and/or if it's a duplication of something that
has already been hashed out on this list.
(I do not have an iPhone, *nor* any [an]Droid,
  so I do not even understand the issues... :-)
This:
http://www.networkworld.com/slideshows/2010/030210-apps-apple-iphone.html#slide16
seems to be saying that it can make possible tethering
in places where the service provider "thought" that they
were making it impossible.
-- 
Mike Schwartz
Glendale  AZ
schwartz@acm.org