Because it's used before the boil, contamination is not a concern because the wort will be boiled before fermentation. If it is caked in crud, then yes, you should clean it.
Primary: Robust Porter from BCS.
Bottled/Kegged: Crappy Bock (my first brew!), IPA, Manny's Octoberfest, Paulaner Hefe-weizen clone (my first all-grain!), Ed's Honey Oatmeal Stout, Dos Equis clone, Pumpkin Spice Ale (my first ruined batch), American Red Ale, Angel Wings from BCS, Edworts Apfelwein, American Wheat from BCS,Terrapin Rye Pale Ale from CYBI, Munich Madness from BCS.