Stop! Before privacy advocates rush to burn twitter at the stake (assuming they’re finished with Google Buzz), please remember this latest move is entirely optional. When logging into http://twitter.com you’ll be prompted with a screen that reads ‘Be found on twitter’ and asks you confirm your profile information.
Twitter say they are aiming to increase discovery of your profile. I already have a public profile, so for me, this was a no brainer – the more followers the better.
Post updated. Thanks to James for pointing out your email won’t be displayed publicly.