Awww .. your disk not big enough for you ? :-)
Have a look at this little toy :
http://www.hds.com/products_services/universal_storage_platform/32Petabytes of storage ... mmmmm ... even I've not played with that much storage before :-) Max I've been running so far (2 years ago) was 240Tb (I think the company has over a petabyte now though)
One thing you need to realise about "big" disks, is you need to have someway to back them up ... so it means spending money on supporting infrastructure ... now before people jump up saying "Well RAID them then!", great that gives you a bit of redundancy, but even a 72Gb drive can take an hour to rebuild if it's full and on a live system, a 5Tb disk would be awful to work with in my job.
For online storage devices most sensible companies these days use 72GB and 144Gb disks, for near-line storage (archive to slower disk ie. IDE/ATA) they'll use the bigger spindles as recovery time is not so critical.
