There are times when it does and times where it doesnt, just the same as in real life.
In a perfect world, we would come in all shapes and sizes, and everyone would be content and happy to be who and what they are. Unfortunately, its not a perfect world, and we are all bombarded by the media, magazines, celeb images, etc. who show us pictures of desirable celebs who weigh half of what an average woman weighs in America, and imply that we must be overweight if you can't see our ribs. Okay, exaggerating, but seriously, the models anymore are rail-thin. I'd love to see clothes in Vogue that would look good on the average person. I'm 5'7", 126 lb. I'm not thin, I'm not overweight, I'm average...but I digress. Anyway, back to the point...
There are loads of sites, forums, etc. that aren't very accepting, or very constructive with their criticism, just as there are critical people in every day life, be it strangers, co-workers, siblings, friends, whatever. Whether they voice to you that your clothes don't match, or your hair is frizzy, or that you have weird teeth, boobs, legs, feet, they're there whether online or in person, and they'll always be there trying to knock you down a peg...whether unintentionally (through great looks, incredible talent, making you jealous, etc) or purposely.
HOWEVER...there are just as many people that want to brighten your day and make you feel great about yourself, even if you aren't a perfect size 2, or have amazing silken hair or perfect skin. The internet is surprisingly great for that, allowing you to interact with people from all over the country, even the world, and show yourself. Take Specktra for example, there is always someone to give thanks for a post, or a sweet comment for a FOTD they like, or a cool pic posted in Say Cheese. The type of women/men on here boost each other's confidence, make each other walk with their head held higher, and generally just make someone's day.