Taken from
xlivvielockex,
here.
Whenever you post an image to LJ, whether you change your layout, post art in unlocked posts, upload new userpics, add sidebars, post unlocked voting in communities, post unlocked pimps in communities, anything image related in public space, it comes up on the LJ RSS Feed. And apparently now, there are several websites that repost the feed, which just links your images. An icon I had in an icontest was hotlinked on the site fuzzysquid and toothpaste for dinner. My views went from a few hundred to over 25K.
To opt out of the feed:
Make sure you are logged into LJ:
Go to the command console:
http://www.livejournal.com/admin/console/ Enter this command exactly:
set latest_optout yes
Hit execute.
This is just to opt YOUR JOURNAL out of the feed. If you want to opt a community that you own out of the feed:
Make sure you are logged into LJ:
Go to the command console:
http://www.livejournal.com/admin/console/ Enter this command exactly:
set for communityname latest_optout yes
Hit execute.
There is nothing you can do about protecting images you post to other people's communities except to point the owners to these instructions.
If you look at the rest of her post, it also talks about photobucket compressing even really tiny images like icons. It suggests saving everything as .png (which you should be doing anyway) because the recompression hurts it less than it would hurt .jpg.