Joseph Weisenthal, with whom I'm friendly, of PaidContent, for which I've worked, writes that the list of sites accepting Open ID is "spare." True. But that Yahoo, which claims close to half a billion registrants, has signed on and bumped up Open ID's potential base an order of magnitude or so, is big news. If people can use one logon, or ID, and log on to myriad sites, such as Six Apart blogs and the contact storing software Plaxo, it bring a utility to the Web that's not there today, allowing one logon and more seamless execution across registered platforms.
With a genuflection to another friend, Daniel Gross, I say this is one of those little things that could prove to be of big import. Whether Open ID or another scheme, open, cross-platform utility is only going to progress geometrically, when it's fast and easy. Now, let me try the thing once it launches and see if it actually works (!).