A WebmasterWorld thread reports that Google Image Search has done an update to their index. One of the members that seems to always be on top of these images updates, zeus, has said that this update is worse off from the one in February.
He said:
Hmm it looks like they are now ruin the good update for 3-4 month ago, now to many images again gets filtered and a lot of images are lost with "moderate search off".
There are many complaints about the new filter in this update at WebmasterWorld. There are also a few sporadic threads at Google Webmaster Help on the topic.
Forum discussion at WebmasterWorld.
