Just bag it. It's the law. Besides, it's the right thing to do. (first in a series of five)
1. Take two baggies with you on a dog walk - one (or both, sometimes) for your dog, and one for one of the piles you find that someone else left behind
2. If you are really brave and see someone not picking up his dog's poop, rush over, pick it up and hand him the bag, saying something like, "Here you go. I used to sometimes forget a bag myself so I've learned to carry several." He will be so astonished, he will accept it!
3. Keep a baggy tied to the hand loop (handle end) of your dog's leash so you always have one. You can also find tiny cloth bags that Velcro on to the dog collar and contain an emergency poop bag or five!
Next: More tips.