I understand what your saying sjinsjca,
Alot of people have negative or questionable feelings about Jailbreaking until you show them what you can do with a JB'd phone verses a Factory Phone and their facial expressions go from

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Lol No lie, I have shown a couple co-workers and the first thing that came up once the topic was brought up was "but cant you break your iphone" hell, u can "break" your iphone by accidentally dropping it down a flight of stairs, or into your drink at the club. but shortly after they see the new possibilities they jump on the bandwagon.
But to get back on topic with your last post,
Apple + AT&T has formed a elite arse partnership, the iPhone has spawned a entire generation of handsets, all these new phones coming out all look like cheap clones of the iPhone.
For iPhone to shut down the JB community, honestly I doubt it would effect them far as sales wise, because the iphone as factory set is still an amazing phone and worth the contract or flat out pay. but the JB community i think is forcing itself to become an important factor in the future progress of the companies software and GUI add on's and updates. like another user said, they can test things within the JB community that if it messes up a phone we will say to ourselves "Ok, I'll just re-jailbreak my phone and not do that one again"
LMAO, I wonder how many people who create apps for cydia are actually doing it under the authorization or funding of Apple. Hell I'll even step out on a branch here and say I wonder if the dev-team is funded or giving additional information from Apple to assist in JB'n and they(Apple) just puts up a front of "Oh, this isnt kool" to keep people interested.
Jailbreak is as close to an Open-Source Phone as one is going to get out in the general public market place. I swear, when Open-Source phone's become widely accepted and available we are probably going to find out that Jailbreaking, Dev-team, Hotz and others were all linked in with Apple some how some way.