Hacking the Pre isn't just about running Doom on the smartphone: it also promises to unlock currently forbidden functionality such as tethering. The Pre Dev Wiki had been one such team working on that, but after a "polite" warning from Palm themselves have ceased publicly discussing it: it seems Palm is concerned, not that webOS might be modified, but that Sprint may demand the manufacturer step in and prevent users overstepping their contracts.
"We have been politely cautioned by Palm 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."
Sprint do not currently offer a tethering option for the Pre, and as such attempting to use it as an external 3G modem for a laptop or other device would contravene a subscriber's contract. If that happened, Palm obviously expect the carrier to turn up on their doorstep looking for the hackers responsible to be curtailed, something Palm doesn't seem particularly concerned about doing themselves.
Of course, we've already seen one hack of the Sprint CDMA Pre which bypassed the carrier's activation and turned it into a WiFi-only device. That can't be something Sprint would find particularly appealing either, especially if it's as easy as reported. This seems a fine line for Palm to be walking: they seem to recognize that supporting - or at least not hindering - fan community tinkering can in fact boost the profile and appeal of a new platform, as happened with the original iPhone, but they of course have to keep on the good side of their carrier partners.