Very true. Standard vinegar will do little to kill weeds. The vinegar used for killing weeds is not standard and is a bit, shall we say, obnoxiuos. Again, as has been mentioned, vinegar is not "selective, it will kill more than what it is sprayed on. Check out organic sites for products that are meant to selectively kill weeds rather than using a concoction that could be harmful to you yourself. 20% vinegar is corrosive and damaging to skin. Vinegar will not kill perennial weeds as it is not absorbed into the root system, it will only kill off some top growth and the perennial weed will resprout. The PH of vinegar is around 2.4.