Other than #temptables, @localvariables and many other objects being stored in tempdb what’s so temporary about it? TempDB is always present on each SQL Server instance and can be a determining factor of your overall performance. In many ways tempdb could be named scratchdb or pagefiledb. The following papers will help you understand what goes into tempdb and how to plan your deployments. These articles are for both developers and administrators.
Working with tempdb in SQL Server 2005
Capacity Planning for tempdb