Depends. At home, I have around 15 or so machines. I would say I have a lot of storage at home. The gateway / firewall servers have 8 gig drives, the file servers have a couple 20gig drives and a 60gig drive. All workstations have at least a 20gig drive. The laptops only have 12gig drives. My workstation has a few 18gig 10k rpm Ultra160 IBM hard drives. Kinda overkill for what I do (browse the www, play games), but appreciated nonetheless.
At work, I have a machine with about 3 terabytes or so. I store just about every build and we have ever and are ever going to make on it. My personal workstation has 5 drives in it. Four of them are 18gig 10k rpm IBM Ultra 160 drives .. and the fifth drive is a Maxtor 60gig drive for MP3s.