Personally, I was afraid to post in the galleries for a long time but now after years, I've started.  I think the intimidation factor sinks in for newbies. When I posted my first vue pic, after nearly 50 hours of work, I received some constructive critique as my very FIRST comment.  It hurt at first, but in all honesty it was well deserved.  I just wish the artist who made the comments had taken time to also tell me what he liked about the picture instead of just letting me know what was wrong with it. 

For people just starting out, I think positive critique is great to encourage them to post more and develop their skills.  Then after maybe a few pics, people might add a comment or two on what could be done better.  It's all in the way its handled and lets face it, some people use kid gloves while others use an iron fist.