Just to correct some posts here, the 360 isn't fully hacked (anymore). The Wii security has been completely compromised to run unsigned code largely because the architecture is so similar to the Gamecube they didn't really advance the protection much.
The 360 DVD drive firmware is completely compromised so that people can pirate games, this is a ongoing struggle between Microsoft and the pirates as Microsoft build new detection methods to ban those going on Live. This is not compromising the main security of the console though which is getting the hardware to run unsigned code. The only way to run unsigned code and hence class the hardware as fully compromised is through the JTAG hack which is only possible on consoles with firmware older than the July 09 update. these are becoming very scarce. While the 360 was fully compromised through this hack there was no master encryption key extracted which means it isn't possible to sign new firmware to run on the console once the 2nd bootloader loop hole was closed. It is more than likely that the 360 will not be hacked again unless Microsoft screw an update up and it opens up another exploit.
The PS3 on the other hand from what I've read has had the master encryption key extracted. There is no way Sony can update this I believe as its hardcoded into the CPU on the PS3 hence the exploit is here to stay. The only thing Sony can do from here on out is apply firmware updates frequently to ensure the exploited consoles cannot go on PSN so it will stop the cheaters that would propogate madly. The big advance the hackers made with this latest hack is if they have the master key then they can probably decrypt the bluray drives firmware on the PS3 now and produce a hack similar to the 360 that would allow reading of copied disks. This would more than likely be easily detectable though so I guess the pirates will struggle to play on PSN.
The information above isn't backed up with links as it is literally my understanding of information I've read over the last few years. In short the PS3 will within the next few months be in the same boat the Wii is in. All in all this day was always going to happen, so full props to Sony on making the device so secure to withstand this length of time, it's still very impressive. The lessons learned this generation by Sony and Microsoft is going to give hackers next gen a real headache as they both so very nearly got it right this time round!