Nope! You may want to add a little sugar to sweeten or some cream cheese or sour cream to thicken it, though. :) It may sound gross, but it actually isn't that bad- especially the sour cream. Sour cream is sooo versatile.
I've done it with strawberries or bananas (or both) with regular milk, a dollop of vanilla and sugar or sweetener added to make it the sweetness you like. If you like the Greek yogurt kind of tang, though, make it 1/2 to 2/3 sour cream and the rest regular milk and add fruit/vanilla/sweetener to taste. If you add too much straight sour cream, it sometimes gets too thick.