Even if you've never signed up for a PSN account, your console will communicate with Sony servers every time it boots up. That initial load process is used to upload error logs, download updates to the "What's New" module, and a list of recently-run applications, including any unauthorized backup manager software.
Sony has yet to ban any consoles for taking advantage of the jailbreak, but the terms and conditions of the PlayStation Network make it clear that Sony has the authority to carry them out. Thanks to the system's constant self-reporting feature, "the company even has the means to irrevocably disable your console should it so wish," rendering affected PS3 consoles unusable, online and off.
Now, I never use the PS3, and the person who does use it has no interest in homebrew or hacking or anything, so it's not a concern... that is, it's not a concern that anything will happen because of anything we've actually done wrong. But it is a concern that someone will simply screw up and poof, there goes your stuff.