Given the volume of PC sales and the way McAfee runs its operation, I imagine there must be thousands of phantom subscribers - folks who signed up once upon a time and left the software behind two or three computers ago.
I favor pocket-sized hard drives that travel between home and office, syncing with computers on both ends.
Most computers today have built in backup software.
Dell fills its computers with crapware, collecting fees from McAfee and other vendors to pre-install 'trial' versions.