Our house has a front lawn that opens directly onto the pavement (no fence). Every night at around 10pm a man from further up the road lets his 2 dogs use it as their loo before they head home. I often see them from my bedroom window as we are going up to bed and he generally picks the poo up.
I have, however, on about half a dozen occasions found a pile of poo on the grass in a morning and had to clear it up - disgusting.
I can't be sure it's this mans dogs ( but I am 99% sure) so won't accuse him directly, but wibu to ask him to stop him letting his dogs use my lawn as their loo? He can walk an extra 50 yards and they can use his lawn instead.