And I'd claim that an SSH key isn't one of them. There is only one platform (UNIX-based web applications with application servers) that actually benefits from them, and plenty that don't (Android, iOS, Mac desktop, Win32, this week's .NET desktop stuff, ASP-of-the-week, Windows Phone 7).
As a company that makes money from users, it's to GitHub's benefit to make it easy to use their stuff.