Apple makes their money from hardware -- software sales are just icing on the cake. Sony, however, has to take piracy threats (since even well-intentioned cracking will lead to piracy) very seriously because they make all of their money from software sales.

Sony's ineffectual attempts to lock down the PSP (starting with the last-minute homebrew policy reversal) probably contributed to the firmware hacking community's fervor. However, after the rampant piracy on the PSP platform, I think Sony is going to take any firmware hacks very seriously. Gamers have proven to be perfectly willing to pirate games if given the opportunity.