Ok, so I have mentioned openID several times now but what does it mean to you and me exactly. If you are like me, you probably have different accounts and usernames / loginids on sites like Facebook, MySpace, Yahoo, Youtube, etc. Unfortunately this is still the norm for the most part, practically every site requires you to create an account and username / loginid on their site.
NOTE: A username / loginid is not the same as an account, usually an account includes information like your name, address, etc.
openID is created to address this problem, especially the username / loginid part. The technology is made available to any site and user that wants to use it. With a non-openID site, you are typically asked to create a unique username / loginid, for me it is usually bobngu or bngu, but you are free to choose whatever your heart desires as long it is available on that site. Instead of creating a unique username / loginid, it is also common for sites to ask for your email address as the username / loginid.
However, openID does not use either of those mechanism to create your loginid. Instead, openID uses a URL as your loginid, for example, one of my openID is
http://clickpass.com/public/bobngu (issued by clickpass),
https://me.yahoo.com/bob_ngu (issued by Yahoo).
IMO, this is counter-intuitive for an end user because a URL typically means a site of some kind. When most users see a URL, they usually enter it in the browser to bring up the site. This is not so with openID, with openID, you use it as a loginid – technically you can enter your openID url into the browser also except that sometimes you will see a blank page (for clickpass) or a simple page saying this is your open id (Yahoo).
Here’s an example of an openID enabled site, Plaxo.
When I clicked on “Sign in with Yahoo ID”, I get this page showing my Yahoo openID – I have to previously activate my Yahoo id for use with openID here.
Note that Plaxo redirected me to Yahoo openID login page. Once I log in on Yahoo, I will be redirected back to Plaxo.
I think a good analogy to openID is credit cards. Examples of popular credit cards issuing parties are Visa, Mastercard, American Express and examples of openID issuing parties are Yahoo, AOL. You can have more than one credit card just like you can have more than one openID. You can also use a credit card at multiple stores just like you can use an openID at multiple sites. A store usually accepts more than one type of credit card (Visa, Amex, MC) just like a site usually accepts different openIDs even if it is the same person.
I hope this help explains why sites that support openID are good for you, the end user because it promotes data portability, i.e., using one openID and one password for multiple sites.