Like Willy says, I had my own theory at the beginning also. I thought that the plan had been hijacked and flown to Pakistan. And I thought that the mystery was part of the terrorism of the whole plot - only to be revealed in gruesome fashion at a later date.
However, I know think that they are finally looking in flight MH370's final resting place. I think they have used all of their knowledge, even learning new techniques to pinpoint where the plane is.
And I think that if they ever do find out what happened that it is going to be some kind of traumatic malfunction that caused wide s[read system failures, and that the final arc of the course of the plane was the pilots last desperate act to set the plane on a return course.
Conspiracy theories are often wildly imaginative, and rarely hold up under logical scrutiny. Lincoln, Kennedy, Landing on the moon, 9/11.... conspiracy theories exist about all of these events, and of course there are theories about MH370.
I think that these theories are simply humanity's attempts to bring order to something which seems so out of order. I know that the theories themselves seem like they suggest that there is much disorder in the world, but it is my opinion that what is more disorderly is to realize that at any moment the craziest thing can happen, and lives can be tragically lost.
The theories are an attempt to say that such tragic things can happen only through the coordinated effort of many men. It doesn't seem logical, but the conspiracy theorists are, in my opinion, simply trying to restore order to what they see as a world out of their control.