Good Negative

So recently I've been doing some work on this and that and noticed something. It is very difficult to get a negative comment on something that you've made or done. For example, I made a facebook cover page for something a friend of mine and I are going to launch. I wasn't particularly impressed with the page, but uploaded it and asked for his comment. Nothing- only that looks good. Similar thing happened with a video I made, nothing but no comment or that looks good kinda vibe. Maybe I'm too cynical or something but I simple don't believe it, that or people have lost opinions along the way.
This is very easy to blame on many things, but I think facebook may have a large part to play here. In general only positive comments are socially acceptable. There is no dislike button and negative comments are very often labeled as trolling. The conclusion that can be drawn from this is that the poster only learns what what gets the most likes, but never learns how to improve. I suppose a general comment about how the world is obsessed with getting likes, or being more blunt, being liked. Supposedly it is human nature to want to be liked, but I think the irony is that the people that are truly like are those that have done the most improving and realised that it is not about being liked. I would also like to add that there is a very definite line between useful negative criticism and general negativity. Going to any comments section it is possible to see some general negativity, but when asking those commenters about the specifics or how they would do it is often possible to silence them.
Solutions? I don't like outlining a problem with no solutions, so this is a stab at one (Hopefully you like it...). I've started asking for one negative comment when asking for feedback. Simple as that- there has to be something wrong with everything.
Be Constructively Negative