Setaria sp. possibly. I try really hard to pull it before it goes to seed. I know you wish your neighbour would.

Thanks. Some new (really nice, actually) folks moved into the house this last year. The previous owners took really good care of the yard, but these folks are not. They have small children, so in a way, I kind of understand. But I'll be battling all kinds of annual weeds in the years to come.

S. pumila is the most likely, certainly for me and you as well.