flickr = getty images = fail in terms of keeping any copyright to yourself. Read the fine print before you sign up (facebook's even worse).
anything to do with getty images, if you decide to delete your account BEFORE you delete your photos, getty images will automatically get the ownership of them.
getty images owns iStock the biggest stock photography website so win win for them
personally i do not post my pics in anything higher than 640x480 (not anymore at least) and do not bother with watermarking it. If someone wants a smaller than a postcard print without my knowledge - you're more than welcome.
also no point taking the piss out of others for putting their watermarks on their photos even if they're still learning the whole slr thing. Unfortunatelly things like photography take time to learn+master and the more you play with it the better you get.