While Facebook and Google wage holy war for the soul of the internet, the front line of the battle it seems is the login credential area. Facebook with it’s 100′s of millions of users are really making headway in this category. The premise is simple, for new and existing website designers, you can have your users log in with their Facebook credentials rather than your own unique credentials. What this means is that you as a web designer don’t need to worry about keeping a separate module for username and passwords. The extra advantage is even better, users don’t have to fill up crummy web forms to register for your website before actively participating in them. This has proven to improve the user uptake of your service, because it removes an extra step from your web design, users no longer have to register, they can do a simple 1-click login that immediately pulls data of the social network and then populates that into your website DB.
This means that you can immediately cater to the 100 million LinkedIn subscribers, or facebook 600+ million members by having them perform simple 1-click logins. No web forms, no passwords, no hassle.
Back to the topic though, having a social network login not only makes it easier for users to login it actually improves the hit rate of your site, because if registration is difficult users are going to be turned off even BEFORE they begin to use your service.