When you deploy it on machines with more than four physical cores in each processor.
Microsoft announced late last year that it would make changes to its SKU lineup and pricing when it released SQL Server 2012. Officials . Microsoft also made pricing and licensing changes with the 2012 release, adding a new core-based licensing option for the SQL Server 2012 Enterprise and Standard products, and dropping the server-CAL license model on Enterprise.
The new Business Intelligence SKU, conversely, is server-CAL only, with no per-core licensing option – but has a server license price identical to what the previous version of Enterprise edition cost.
SQL Server 2012 will be generally available on April 1, 2012.
Its not lcear to me yet but it seesm that users could be paying substantially more to license SQL Server 2012 under the new per-core model.