So Send Dialog only allows them to decide to share something on the app. What I'm suggesting is the "post as" feature to also include "message as"
What I'm talking about here is simply this: trusted apps that don't want to spam your wall but that would be made more useful by allowing direct notifications to OTHER Facebook users.
To me, this is intrinsic to Facebook becoming the social layer upon which all other applications are built.
No, there's no single 3rd party app that I trust as much as Facebook. I don't know who most of these these 3rd party developers are most of the time, and that unknown makes me distrust by default. Not to say I wouldn't use a FB app that provided a service to me that I desired - I have, and I do. My original point was that I don't think I could ever trust an app enough to be able to send private messages from my name without my consent to do so - every time it wants to. The few apps I do use have greatly restricted permissions from what the app developers originally asked me for.
However, don't let that comment drive the assumption that I inherently trust /Facebook/, either. I don't. I use FB with the clear understanding that they only know about me what I choose to tell them about me. I don't put anything on Facebook that I wouldn't print out and tape to a telephone pole as public information.
I don't use FB chat. Not because I inherently distrust it - I don't inherently "trust" it either, but that's not primarily why I don't use it. I just don't have a use case for it. Likewise for messaging - I don't have a use case for it in most cases. Why would I give my private messages to Facebook when I can just send an email to the person directly?
I tend not to use mobile FB apps either. Again not necessarily as a matter of trust but as a matter of use case. I usually just access it via browser, so I don't have any real reason to use a specific mobile app - I've tried them, and none of them really seem to be any better of an experience (to me) than just hitting the browser version.
So I've yet to find a compelling reason to trade my trust for a product or service through the platform, and frankly, it'd have to be a pretty awesome thing for me to make that trade-off.