Column-oriented databases are the next big thing for data warehouses, having passed through object databases for specialized applications. For a while, InterSystems Cache enjoyed the spotlight as a high performance object database. Now, Vertica is the hottest thing the database world has to offer as a column-oriented database.
Column-oriented databases store column-data as a contiguous sequence, as opposed to relational databases which store row-data in contiguous allocation units. This makes it simpler to make schema changes, and offered better performance for OLAP applications. Relational databases still are the best solution for general purpose OLTP applications so it isn't the end for them yet, although they were architected almost three decades ago.