1. It makes it easy for anyone to import hundreds of images from Flickr (via Photoset importing), which could mean a big increase in Flickr-washing problems (i.e. unintentional copyvios).2. The feature still has some bugs (https://bugzilla.wikimedia.org/show_bug.cgi?id=43450) and no one is actively maintaining it at the moment (although hopefully the new Multimedia team will be assuming that responsibility).