"Rant Alert Captain...."

Thank you Spock.
This is a limited year round problem; however at holiday time it's much worse when vizturs are around. Poo bags hanging off trees, bushes, left on those pretty convenient walls, "To be collected on my way back...." But they never are.
If you see anybody do this, politely ask them to take it with them or just leave the compostable poo where it is, so the natural thing may occur. 
"Yes dear I took the little blue one......and the green one."