Is more irritating when it's an annoying song form an advert (go compare anyone!) or chiristmas songs in April!
+1 - I had the song from the Lurpack advert stuck in my head a few days ago "chop, chop, chop, chop, chopping! slice, slice, slice, slice, slicing!" Grr! 
I went to Rock n Ride spin class this morning, lots of 80s stadium rock ... now I've got You Give Love A Bad Name by Bon Jovi stuck in my head - much better than Lurpack! 