The most common reasons for a blown light bulb include either cheap bulbs, loose connections in the lamp holder, a loose spring loaded connection in the bulb or a loose light switch. When the connections are loose, the electricity causes an arc, which produces more heat in the fitting and causes the bulb to blow.
Cheap light bulbs blow more often due to the thin materials used in creating the bulbs. With the thinner material, the bulb is more likely to blow even with a slight surge of power.
Arcing electricity melts the metal it arcs to, so when bulbs are subject to arcing electricity, the bottom of the bulb often shows signs of indentations.
When a light bulb blows, the fuse or lighting circuit generally blows as well. The blowing lamp causes the main circuit breaker to trip because the thinning elements of the lamp cause momentary overheating causing a current surge that the main circuit breaker notices.
In instances where light bulbs continue to blow, the bulb supplier, wire connections inside the bulb holder and spring loaded connectors inside the bulb holder need to be checked. The light switch is rarely the problem, but if the other factors are not causing the blowing bulbs, the switch should be checked.