The Laser Tripmines are one of the cooler weapons seen in Half-Life. Used to booby trap areas, or prevent access to certain locations, the tripmines are, in all truth, rarely detonated. Since the laser is quite clearly visible, it is a rarity that a player will just walk on over them. However, netting is a skill that can be quite effective.
Most players consider the skill of netting stupid, and over used.
However, if done properly, netting can be a multiplayer technique that will score you kills. Since a tripmine is rarely detonated, when it is, it usually doesn't even score a kill. So therefore, it is obvious to agree that setting more than 1 tripmine is much better. Now there are different ways to use netting. When running away from an enemy in an online server, you can quickly set 2 tripmines blocking a doorway that you have just walked through.