From WebOS Internals
We have been politely cautioned by Palm (in private, and not by any legal team) that any discussion of tethering during the Sprint exclusivity period (and perhaps beyond—we don't know yet) will probably cause Sprint to complain to Palm, and if that happened then Palm would be forced to react against the people running the IRC channel and this wiki. There has been no legal action of any sort.
We want to retain a good relationship with Palm, since we believe that will be better for the whole developer ecosystem in the long run. For that reason, we are not allowing discussion of tethering on the IRC channel, or in this wiki. There is no secret agreement with Palm, and the IRC channel and this wiki receive no special access to any information from Palm that is not publicly available already. This development group has simply decided to take a stand and do things the right way instead of violating legal agreements.
Note that Sprint does not have a plan available for use with the Pre which allows tethering under the Terms Of Service.
Once there is a version of the Pre available for a carrier that does allow tethering, or an unlocked GSM version, we may be able to change this policy.