It's all about placement. I use tac Inserts a lot when I play demolition. What I have seen a lot of people doing is planting the tactical insertion right next to them, or in the same room that they are camping out in. That is a big no-no. You plant your tac insert in a separate, nearby room and then if you do die you can come back and surprise the guy who killed you. A lot of campers find a great camping spot (like the roofs or cranes on Highrise) and plant tactical insertions up there so they can quickly get back to the spot.

It's much like claymores, people are placing them at the wrong angles allowing people to either see them, or to run right over them once they here the click. Claymores really need to be planted inside to the corner of the doorways, not directly infront of doorways. They can also be right around corners instead of at the corners. Most people slow down right when they turn around corners so it's a great trap.