let me put forth a few legitimate reasons to hack the ps3.
a better web browser, ps3 hardware and THAT is the best we can get? my old p2 333mhz ran the internet better than that.
video codecs. there are allot of videos out there, and the best encodes for said videos will not work on the ps3, at least as of the last time i cared to check.
the over whelming power of the ps3 alone. a home brew (lol yea homebrew, but im being serious when say that) could open it up to people who never even knew about them. imagine this. what if sony came out and allowed homebrew to some extent, instead of forcing their psn network (i hate the way its setup and functions) and allows people to put what ever they want on the console. hell even a minecraft like game where you pay for it would be a run away success for them.
jailbreaking it can lead to pirateing, but saying because of they you take away all functionality is a dangerous thing.