From this altitude it looks to me like live oak seedlings or offshoots from the roots of a live oak. Any chance of that?

Definitely not offshoots. My yard backs up to a wooded area so there's no telling what sort of seedlings hit my yard throughout the year.

The weed has very shallow roots if that means anything.

I have the same weed in my Bermuda in Greenville, SC. It's just starting to show up in my back yard. I have no idea what it is, but I had it last year also.

From a distance, these do resemble oak saplings, but not so much in the close-up.

It appears that it grows faster than the grass. Does it come back if you mow over it? I have a few trees (that no one locally has been able to identify) that drop berries during the winter. Usually in early summer, they will begin to sprout into little saplings.

Initially I tried to pull them, but I soon realized that it was a losing battle. Instead, I just mowed them down which would kill them. Usually after about two to three weeks of mowing they stop sprouting until the next season.

I don't think these are any type of tree, but they aren't a grassy type of weed either. So if mowing would remove enough of the leaf structure it might be enough to kill the plant.

They are definitely not from a tree, and mowing doesn't seem to slow them down for me. They are extremely easy to pull out of the soil, and they do grow fast.

Checking out some sites online and I think it resembles "poke weed."

Ditto to what prorange said. The only thing I don't know is if mowing slows them down. Last year I sprayed or pulled them before I could see if 2+ weeks of mowing would eliminate them. I didn't have the patience for it. Hopefully the weather will dry out enough for me to mow sometime this weekend. I am using a reel mower this year so I should be able to cut off the majority of the leaf. Once again, I have no patience so if it looks like they are growing back, I will spray them sometime this week.

I looked at weed ID sites last year and thought it resembled pokeweed or pigweed. I got so frustrated last year I pulled some and took them to my county extension office. They couldn't ID it either. My guess is it's a perennial and not an annual which is why my pre-emergent isn't touching it. I have no idea how or why it started growing in my yard last year out of no where.

Prorange, I STRONGLY recommend Ortho Weed B Gon for southern lawns. I used the concentrate form and mixed it in a tank sprayer. I diluted it with water a tad bit more than what the directions specified but the weed was dying within 24 hours and the damage to my grass was minimal. This stuff works fast and it works well. Good luck!!!!