Jetties @ Inlet Beach?

Those might have been the experimental "groins" that were in place for a while. They were a test of an alternative beach renourishment technique, trapping offshore sand.
Google's aerials are not current. The project was a while ago.

That's good they are gone. Are there any drawbacks to this area? It seems very underdeveloped compared to the rest of 30A.

Inlet Beach was developing rapidly until recently and will do so again. The only drawback I know of is that it is on 98 rather than Scenic 30A, which gives it a different character. It also makes the area north of 98 more residential as opposed to mainly rental.