Douglas Alpenstock wrote:"Weeds are not always the enemy" -- YET!
A long while ago I had a great harvest in a situation with extreme heat and drought; because chickweed flourished and provided shade and held moisture. And I was busy and let it go.
Next year, chickweed thought it owned the place. I still like chickweed, but I know its nature. "Give a thief your finger and he will take your hand." Watch your alliances for treachery! 
I love chickweed. It's low, shallow roots, and dies a natural death in the hot summer. I let it go wild this spring, just cleared off the hills where I planted corn. Where the chickweed was left growing, hardly any other weeds grew. I think it protects the soil and eventually adds nutrients when it dies.
This year I am letting a lot of low 'weeds' grow between the rows. Dandelions, clovers, chickweed. I suspect they will take away some nitrogen this year, but in coming years will become a net gain. I even scattered some trefoil seed today on some bare ground. Definitely going to work on getting that established.