How Big is Big? Oracle's Largest Data Warehouses
I found this post, entitled Some of Oracle's Largest Warehouses, on the DBMS2 blog and I thought I'd re-sort them by size in descending order. So, here they are:

Quoting Curt:
Exadata
While I know it's a bit unfair to compare contentbases with databases (because content is generally so much bigger and there is so much more of it), I thought I'd point out that the largest MarkLogic production application today runs at over 100 TB and that a typical publisher has single-digit terabytes of content. And we're just getting started. And we're not storing lots of stuff redundantly to optimize performance as you would in a data warehouse.