Some people maintain that a tarp edge flapping wildly in a strong wind is more likely to tear because of the varying stresses on the tie-out points. It may also be more likely to pull stakes out of the ground. I don't know if these things are true, but the noise of a flapping tarp can be irksome. I recently added cat cuts to the sides of my cuben tarp because I could see from the wrinkles that develop with use that the stresses were greatest angling up slightly from each tie-out. Doing a cat cut puts the reinforced tarp edge more in line with those forces (I think). I plan to add cat cuts to the ends of the tarp, too, because I think the sides look better.