Gwen I have, with quite a shock, found out that Flickr gives 3rd parties complete access to you pix through their API.
I used Flickr’s “security measure” that disallowed people to download the larger versions of my pix and also discourage them from merely right click and copy with their “spaceball” feature…thought this will be good enough.
Then I found my pix on various websites, all over the web….and not just the medium size, the large versions that is not suppose to be seen by the public….and anybody is able to copy it. I took this up on the Flickr help forum….they told me that this is the API that any 3rd party can use. Flickr “requests” 3rd parties to adhere to the privacy setting of Flickr member, but it is just a request.

Through the API the 3rd party do not host the pix….the API just allows your pix to become searchable….but on the 3rd party sites it is very easy for somebody to copy your pix…including the large versions….this is how my large versions ended up on other sites.
Ironically, the thing many Flickr members “chase” after, namely Explore, draws the attention of these 3rd party API users to your stream.
I was told the only way you can avoid ending up on 3rd party sites through the API is to make your pix private.
On Facebook I now put HUGE copyright signs right in the middle of my pix and on Flickr I only upload small, low quality versions viewable to the public…the larger version I add as a private pix.
@ H. erectus…I take pix for exactly the same reason….I want to share with the world.

But I did get upset when I found out that people are using my pix without my permission….some of my pix even ended up being sold on places like online greeting card site etc, etc. Many of those pix took time, patience and effort….I do not want to sell my pix, but I do feel ownership…they are still mine.
@ tiggercat…you will be surprised at what pix get stolen. Those pix of mine that were discussed in the other thread about stolen photos, were mostly very bad quality photos. It is often the content, not the quality that counts.
@Touareg …don’t stop posting your photos. Just post them at low quality with a nice copyright sign on or very close to the subject. Most people will understand why it’s there and will look past it, still appreciating the photo.