I was in love with the idea behind open id and the possibilities. As the title suggests I think there are more cons to using open id than pros. This really came to light after a client requested it and we were looking into integrating it into the site.

Cons

1. The implementation is not consistent between publishers. I have experienced problems utillizing yahoo ids with my early experiments which I have written about here
2. Including open id support in existing login/registration workflows are less than ideal.
3. Can be used for spamming, see t his post  http://robrohan.com/2008/10/31/openid-maybe-not-as-cool-as-i-thought/
4. The open id is not easier to remember that the usual username/email people are accustomed to.

Pros

1. Open Id strives to allow users to maintain one set of authentication credentials that can be used across multiple sites.
2. The open id spec accommodates retrieving useful data from an open id provider. This means that if I allow a user to create an account on my site using their open id i can retrieve some information from their id provider like first name, last name which I can use in my system (though no provider I have tested so far does this).

There are probably other pros on the site but I think these two are of particular interest. I don’t think we’ll be including open id in  our work just yet because their isn’t much value in it just yet. There is only one site that I think has gotten openId implementation correct