Yes, sometimes we do have to trust. And, without being gullible, I personally dont have an issue with that, in this instance. IF something nefarious happened with MH370, there will be a darn good (and scary) reason why we are not being told and a multi-million dollar cover-up is in place.
However, I do not believe a cover up is in place. There are many other ways to cover up .. like .. just not search. Just say "we dont know where it could have gone .. we've looked in the obvious places, and if we can ever figure it out, well search again".
They have said many times that the locale of the plane is believed to be where they are searching due to Inmarsat and other data .. they just have not revealed all that other data imo. Nor should they have to, if it is a matter of security ... again imo.
I don't think there is a huge conspiracy, but I believe in as much transparency as possible. I still think there could be something terribly wrong with the Inmarsat data and if they have other data to support it, then I believe they should reveal more of that. I am just not buying that it's so secret it will harm anyone's national security. I think it's just coming down to politics and egos more than real security issues.