Lol....yeah, standards aren't especially high in social media. I see crappy pics al, the time with terrible filters on them ala Instagram and comments like "wow, you're an amazing photographer" or "you should be a photographer" and I'm all, wtf, that looks like total S___.
At the risk of sounding snarky... Duh, its a SOCIAL site. People go there to be social. People, in social situtations, generally are not critical but supportative.
When you are invited to someone's house and they ask you "What do you think of our new drapes?" What do you say?
If they are a friend, you say "looks nice" even though inside you are cringing.
Protip: When someone, in a social situtation, asks you what you think of something, they are not really interested in what you think about it.
If someone takes the time to post a picture on a social network, there are only two socially acceptable public replies.
1. Find something nice to complement the photographer on the photograph
2. Don't reply at all.
I like sharing pictures on Flikr. I always adopt the schema of complementing in public, and only if necessary, offering a critique via private mail. I rarely critique photographs as it really is up to the photographer to be freely able to express their art as they see fit. Its a social site, not a technical photographic evaluation service.
Now if someone specifically asks me to critique their photograph, I will offer them my opinon, but in private. That way they can either take my opinion as advice or not and no one is embarrased.
When it comes down to it, we need to recognized that our opinions are not as valuable, to others, as we may think.
If Sally tells John that John really should be a professional photographer, and I disagree... so what? Sally is paying John a social complement. It is really not worth getting upset about.