Realistically, the PS3 is (probably) as weak to the original hack that worked on both the XBox 360 and Wii where the disc-drive was "tricked" into thinking that a writeable disc was an original game disc ... the problem with this is that you still need the disc image to retain its signing, and Sony's immediate reaction to this would be to release all PS3 games on dual-layer Blu-Ray discs and to fill all the space with garbage before signing the image. While people might be willing to download GTA over a 4 week period its unlikely that you would get many people that motivated to download other games ...
Beyond that, the secondary problem is that (even with getting the PS3 to play unsigned games) it has the same problems that kept the Gamecube from being modded for so long ... The disc format is expensive enough to lower the percentage of people interested in stealing games, the userbase is small, and there is more money in making a better mod for another console than there is in cracking the PS3.
Edit: There is one other thing that has limited PS3 hacking ... (For some unknown reason) there are several really smart people who want to run linux on everything, and since the PS3 can have linux installed on it these people where not looking to find and publish exploitable hacks which are (often) turned into viable mods.
