And what if they don't want a Twitter account?
While this undoubtedly does save the programmer some time & effort, as well as pawning the responsibility for privacy of user information onto the other service, it makes 2 huge assumptions:
1) That the people who want to use your application have a Twitter (or other social website) account, or are willing to set up said account just for the privilege of using your app; and
2) They're willing to use their Twitter (or other account) to use your app.
Sure, it's not that big of an issue if the web developer is trying to come up with the next social media app, because the assumption is that you're targeting the social media users & wanting your app to be found on that particular site. However, this article seems to be aimed more at "independent" web developers...i.e. those trying to develop a site that provides unique content for the users, but not necessarily tied into a particular social media site. And given the privacy concerns that certain sites (*cough* Facebook *cough*) have had recently, even people with social media accounts may not want to have their social media account tied into a non-affiliated website.
Or, to look at it another way... why would I sign up for a message board where people can discuss FPS games for PCs, when it wants me to use my Yahoo email username/password to log in? There's no need to tie them together -- especially when it would have been easier for the website creator to simply create a Yahoo! Groups site (thereby justifying the use of my Yahoo ID) since it allows them to control who joins the group.
