Jailbreaking is totally reversible. The method they released is flashing the baseband to an ipad baseband which is not reversible and apple will be checking for that baseband on iphones sent to service.
Also i don't even own an iphone 3g or 3gs, i am only posting this because many people doing this process are not aware of what it imply.
I understand your point and i agree.
I think they should put more emphasis on the voiding warranty part and the unability to restore to a stock firmware, because right now this information is hidden in a big wall of text.
I'm not saying you can't make the phone look like new, I'm saying you've alreadyvoided by the warranty by jailbreaking, the fact that you can hide it from Apple is irrelevant. If I use a cracked version of software am I not committing a crime because the developers don't know? I hardly think so. If you want to do it, fine, but don't claim you're somehow reversing your original warranty voiding action because you changed it back before Apple sees it.