Hi Sugar Mama, Zombie is right you can use salted in a pinch. But unsalted is what you should strive for. It is usually understood in recipes that for baking you use large eggs and unsalted butter. Salt content varies by brand and it would be nearly impossible to balance extra perceived saltiness without compromising the texture of the frosting. Unsalted butter also tends to be fresher as salt is a preservative. Enjoy your buttercream!

Unless you're going for a salted caramel taste, I'd get unsalted butter for all your baking.

I always use salted butter in everything I make and I make around 15 cakes a week..all delicious with no complaints! Salt brings out the flavour of all foods after all

I prefer unsalted myself because the amount of salt in regular butter doesn't seem to be too consistent. That being said, if I don't have any at home, I use regular and it still tastes great!

The gold standard for buttercream is one made with unsalted butter. I agree with ChefJune that using salted butter definitely affects the taste.

Definitely unsalted.