Daytime Use
Laser sights are typically available with green or red laser beams, with red dominating the marketplace. Unfortunately, the laser beams of the sights lose their effectiveness in brightly lit conditions, such as daylight. In typical daylight conditions, the red laser becomes virtually invisible, rendering it useless as a sighting reference. Green lasers are generally easier to see in well-lit conditions than their red counterparts; however, they can still be difficult to track in high ambient light.
Learned Reliance
Depending on a laser sight as your primary aiming reference can detract from developing your natural shooting abilities. Accurately shooting a handgun is a skill built on your natural hand-eye coordination; by relying on a laser beam to determine your point of aim, you can begin to depend on the laser rather than developing your own natural skill. This dependence can be extremely detrimental if the laser becomes inoperable.
Position Giveaway
One of the greatest advantages of a laser grip inadvertently causes one of its greatest disadvantages, that of position giveaway. The greatest advantage of a laser sight is the intimidation factor the laser can project onto a potential assailant; the appearance of a laser beam indicating the point of impact of a bullet can, and often does, cause a bad guy to take on a less-threatening demeanor. However, if your intention is to remain concealed, the laser provides a direct reference to your position, revealing your location.
Reliance on Batteries
Laser sights are electronic devices that rely on batteries, generally lithium. As such, laser sights are subject to dead batteries or other electronic failures. Grip laser sights are designed to be waterproof and shockproof; unfortunately, this cannot guarantee that the laser will operate under any condition. Consequently, any event that renders your sight inoperable will really affect your accuracy, provided you're using the laser as your primary sighting reference.