The Laser Tripmines are one of the cooler weapons seen in both Half-Life and Opposing Force. 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.