I fiddled around with a similar concept a couple years ago. I got the best results using 2 corkscrew shaped dog tie-out stakes. It worked fine in the back yard. It even worked ok when I set it up on the beach one day. But I had two miserable failures at SEHHA hangouts.
The first attempt was at the Rainbow Springs hangout. The soil there was so thin atop rock that I couldn't get a corkscrew more than a couple inches in. I actually twisted the top of one corkscrew stake right off trying to work it in (lesson: there's a big difference between the aluminum tie out stakes sold at the dollar store and the heavier and more expensive steel ones sold at Petco.)
The second failure was in Hot Springs. The mix of sand and decaying organic duff soil proved to hold very poorly. I eventually found a spot further from the river that would hold, but I was very, very careful getting in and out of the hammock that weekend.
So for a backyard hang? Fine, go for it. It's a lot easier than planting two trees and waiting for them to grow. But for car camping? I wouldn't rely on it.