There are few people who personify their companies like Steve Jobs. The only person who even comes close is Warren Buffett. Steve's resignation from Apple is definitely a blow to the company, this guy is truly a visionary. As this article put it "Steve Jobs is perhaps the most successful brand manager in history, and he did it, paradoxically, by embracing the precise corporate values to which the Apple brand identity is ostensibly opposed."
Like Google's "Don't be evil" culture, Jobs has created something very unique at Apple - I hope it can continue without him at the head.