Still, keeping a private key safe for a distributed corporation will be a challenge. One attack I can think of - set up a fake hosting company that claims to offer cheap hosting, wait for the corporation to move some of its agents there, then bam, you've got the private key. That kind of thing might be difficult to pull off, but if any of these corporations controlled significant assets, then the amount of resources an attacker would be prepared to expend would be very high.
I suppose it suggests a mechanism where spending resources requires the cooperation of a number of agents that must be contracted with different hosting companies, and perhaps a period of warm up, where for the first x months, an agent might do useful things but would not be given power to control money.