Right, I remember you used to be able to sign up for Twitter solely with a phone number (and post tweets via SMS, a feature which I used every so often). You c

Right, I remember you used to be able to sign up for Twitter solely with a phone number (and post tweets via SMS, a feature which I used every so often). You can see that if you look at an old archive of the site: https://web.archive.org/web/20061203201128/http://twitter.com/ https://web.archive.org/web/20061203201128/http://twitter.co... (heh, also gotta love that the site was so small they can just show some random recent tweets and users right on the homepage) This was in the days before legit smartphones so running an actual "twitter client" was out of the question. Of course that all quickly changed with the advent of smartphones like the iPhone.