1. The major drawbacks to hydroponics

2. Wick system- the biggest draw back of this system is that plants that are large or use large amounts of water may use up the nutrient solution faster than the wick(s) can supply it. 
Water culture- the biggest draw back of this kind of system is that it doesn't work well with large plants or with long-term plants.
Drip, flood and drain and n.f.t. are all subject to power failures.

3. The effects on farmers
If hydroponics becomes a major part of the agricultural world then farming as we know it today will no longer be.
All the tractors and farm equipment will be gone and the farm land will become houses.
All of our food as in veggies will be grown in water and a greenhouse.