Flicker API: exclude picture with a certain tag?

Im playing around with this piece of code from http://api.jquery.com/jQuery.getJSON/ (see code example further down, pictures with the cats). What i want to do is specify multiple tags, but exclude a certain tag. At http://www.flickr.com/services/api/flickr.photos.search.html the flickr docu states:

tags (Optional)
A comma-delimited list of tags. Photos with one or more of the tags listed will be returned. You can exclude results that match a term by prepending it with a - character.

However this doesn’t work for me:

<script>
$.getJSON("http://api.flickr.com/services/feeds/photos_public.gne?jsoncallback=?",
{
	tags: "sydney,cairns,roadtrip,-travellersautobarn",
	format: "json"
},
function(data) {
	$.each(data.items, function(i,item){
	  $("<img/>").attr("src", item.media.m)
				.attr("alt", item.title).attr("title", item.title).appendTo("#images");
	});
});
</script>

Firebug shows that my API call looks like the following to exclude a certain car dealer who keeps … erm… “promoting” within those tourist destinations:

http://api.flickr.com/services/feeds/photos_public.gne?jsoncallback=jsonp1322818492147&_=1322818492160&tags=sydney%2Ccairns%2C-travellersautobarn&format=json

but i still get his pictures in the response (see items -> tags ). Has anyone a solution for this, or can tell me what i’m doing wrong here? If i could exclude this guy via user_id this would probably also solve the issue for me.

Is he tagging the photos travelersautobarn? Or is that just the user?

PS: In either case, I would probably redact this on my side of the web service unless he stuff so many photos in the stream that you are declining more than you show.

Hi and thanks for the reply,

Both - he has a user with that name, and adds his brandname to the tags and watermarks all the images with his logo - big enough so you even still recognize it on the thumbnails.
I may have to play around with the tags to find more generic ones.
Dont think i could exclude the pictures via js on the client side since the number of pictures i get from the api call is quite limited (20?); and eventually i wont find any matching pictures.
Open for other suggestions …