A definition of a loaded question might be: "Any question with a hidden agenda or hidden assumption." The classic example is "When did you stop beating your wife?"
For my perspective, loaded questions have mostly a negative effect. When we hide, others hide, and the result is a bunch of posturing, As I am interested in Truth, I find little value here.
The main value of loaded questions are that they are provocative. They are more likely to get answered and start discussions. But are the discussions of any value? Is any learning or growth going on?
In terms of identifying a loaded question, some are easy. Others are hard. The easy ones contain self-contradiction, stated falsehoods, or suspect statements. The hard ones seem to be of two types: One is feigned innocence. The other requires a knowledge of the assumptions about the situation, some background that is represented in an off way.
Some questions are accidentally loaded, as when a person means a legitimate question but uses an incorrect term.