Only for $20/month. There are things you can install on your Android (even non-rooted AFAIK), or on your jailbroken iPhone, that let you tether to your normal non-tether dataplan.
(At this point you can happily complain about morale or market issues relating to stealing that bandwidth; for the record: I pay the $20/month and am quite happy to do so.)
True, but there's a big difference between "jailbreaking makes these things possible, where otherwise I would be screwed," and "jailbreaking lets me get things for free that I would otherwise have had to pay for." The GP appeared to be about the former.
However, a data plan that does not allow tethering is a carrier issue, not a phone issue. Here, tethering is included with virtually all data plans, across all of the major carriers.
(At this point you can happily complain about morale or market issues relating to stealing that bandwidth; for the record: I pay the $20/month and am quite happy to do so.)