No. They’re called nucleation sites. These are microscopic imperfections on the inside of the can. When you shake the can a small gas bubble might form there and after that more CO₂ can diffuse into it until the bubble grows large enough to detach and rise. A small pocket is however left behind, so the same site keeps making a steady stream of bubbles. These are what cause the can to immediately overflow when you open it. Tapping the sides before opening causes these small trapped gas bubbles to detach and rise to the surface and then it can be safely opened. If it haven’t been shaken, then there’s no need for this, though there’s no harm either.
No. They’re called nucleation sites. These are microscopic imperfections on the inside of the can. When you shake the can a small gas bubble might form there and after that more CO₂ can diffuse into it until the bubble grows large enough to detach and rise. A small pocket is however left behind, so the same site keeps making a steady stream of bubbles. These are what cause the can to immediately overflow when you open it. Tapping the sides before opening causes these small trapped gas bubbles to detach and rise to the surface and then it can be safely opened. If it haven’t been shaken, then there’s no need for this, though there’s no harm either.