[indyalex]

Tethering has been around for many yr's..I think the best way to answer your question the way it's worded is:when the Everything plans came out in 2009 there was no provision or add on that allowed for tethering,also known as Phone as Modem(PAM) as was the case in the past with the older plans.
I have the Everything data plan,so I can only assume those still on an older (non Everything plan) that have a free or pd.PAM add on still can (grandfathered),but the codes are no longer available to add now, from what I understand.
The problem is since the Everything plans came out there is no offering of PAM add on thus forcing anyone who does tether to be in violation of the Sprint terms/conditions of their contract,and thats why people sometimes refer to them(Everything plan) as not so everything plan.Of the newer plans the only deviation is the Bus.plan do still have the provision for PAM.
Now to confuse this issue even more there have nearly always been 2 types of tethering if you had a data plan(prior to the Everything plans),you either pd.for it as an add on or you did it without paying for it by manually disabling nai or by having a purchasable after market software such as PDAnet which did it for you thus flying under the radar so to speak.In fact the latter can still be done but is a violation of the T/C of Sprint's contract.
Yes it can be even more confusing if you have the new EVO because Sprint does offer the $29.99 Hotspot plan add on(which is above & beyond the Everything plan & $10 add on requirements).The EVO Hotspot enables the user to connect the EVO ph. to a max of 8 devices(WiFi).Now the really confusing part is if you use the EVO to tether (without the Hotspot plan) you still are in violation of the T/C even though you are paying the $10 add on EVO fee.
Beyond this exp.if you still have questions Sprint cs will have to explain the EVO fees and such because I simply can't/won't attempt to explain or justify it.I hope this helps though.