Tethering is becoming more and more a taboo for mobile phones, I can understand the issue for operators that offer "flat" rates for phones, a PC produces more traffic than a phone (even though with latest generation of smart-phones the gap became much thinner) and I agree that an operator can offer a phone with a discounted "unlimited" data plan in exchange of locking the phone tether ability. But the unlocked version of that phone must have that feature enabled because most operators offer "tether aware" data plans.
My operator charges for real traffic usage (actually I do pay a monthly fee for having 500mb "free" each month) and a megabyte its the same if it is downloaded from a phone or from a pc, so tethering make no real difference for them, so why it have to make difference for phone producers?.
More and more smart-phones (ex the Motorola Milestone) came with no tethering ability, or with other features removed because "the user doesn't need them" or because "this is a business terminal" and other justification, but it is the user that knows what he/she needs and every user have it's own "unique" needs, so companies have to produce items that are flexible enough to satisfy most of them, it is the phone that have to adapt to it's user not the opposite.
Actually seems that a fraction of users (let's think that we are speaking of 35% of world wide users) lead the companies decisions for everyone, so we have dozens of mobile phones that are just clones of each other (with different chassis styles) same cpu, same features, same limitations; there are many devices with "huge" usability flaws due to "stylistic" decisions, or full of dozens of features that you will never use while missing the one's you really need, for example I don't need facebook or twitter integration in my phone, but I DO need tethering and a qwerty slide-out keyboard.
Why all the other have to adapt? Can we have phones that suite all of us?
Let's hope the term FLEXIBILITY will become the new slogan of 2010 for phones.