Pascal Van Hecke – Daily Links

"Robots.txt has been with us for over 14 years, but how many of us knew that in addition to the disallow directive there’s a noindex directive that Googlebot obeys? That noindexed pages don’t end up in the index but disallowed pages do, and the latter can show up in the search results (albeit with less information since the spiders can’t see the page content)? That disallowed pages still accumulate PageRank? That robots.txt can accept a limited form of pattern matching? That, because of that last feature, you can selectively disallow not just directories but also particular filetypes (well, file extensions to be more exact)? That a robots.txt disallowed page can’t be accessed by the spiders, so they can’t read and obey a meta robots tag contained within the page?"

Eran Hammer-Lahav compares "Sign in with Twitter" versus Facebook Connect (on is based on standards, another isn't) and sign in with Twitter versus OpenID: the first makes sense as additional _identification_ on top of already existing authentication. Or: It only makes sense to add the button if you have implemented Twitter Oauth and really do something with Twitter functionality. If you just want anyone to log in, use OpenID.
Yet: Twitter is not an OpenID provider yet, so a lot of people will implement this as an extra "proprietary" OpenID…

Could become a popular alternative to signing in with Facebook Connect, Friendconnect or OpenID.
Just unclear to me why not become standard OpenID provider – OpenID popup also is just one click…?