Stewart Butterfield at Flickr announced today that there are going to be major changes to the way that the Flickr API handles authentication. Apparently the current method will overlap with the new method (which looks pretty robust and secure). This is going to change the way that every method that requires authentication will work. I'll implement the new system as soon as I can and stuff it into the next release. As far as the methods go, I'll try to make the change as transparent as possible. I'll post more on how it will work out with their new system when I've had more time to look over it.
Of course, if you're not using authentication in your web application, you won't need to redo anything at all.