<p>So I'm not quite convinced about OpenID yet, and here is why:</p>

<p>I already have an OpenID because I have a Blogger account. But I discovered that Blogger seems to be a poor provider when I tried to identify myself on the <a href="http://altdotnet.org" rel="nofollow noreferrer">altdotnet</a> page and recieved the following message: </p>

<blockquote>
  <p><strong>You must use an OpenID persona that specifies a valid email address.</strong></p>
</blockquote>

<p>Lets forget the details of this little error and assume that I want to change to a different provider. So I sign up with a different provider and get a new, different OpenID - how would I switch my existing StackOverflow account to be associated with my new OpenID?</p>

<p>I understand this would be easy if I had my own domain set up to delegate to a provider, because I could just change the delegation. Assume I do not have my own domain.</p>

Ideally Stack Overflow would allow you to change your OpenID.
OTOH, ideally you would have set up
OpenID delegation
on your own site, and used that to identify yourself.
With delegation, you would need only change which service you delegate to. You'd still be identified by your own URL that you control. But that doesn't help now unless Stack Overflow lets you change it. Most sites tie OpenIDs to real accounts, and would let you switch or at least add additional OpenIDs. Doesn't seem like you could map OpenIDs to accounts 1:1 unless the result of access is totally trivial; otherwise you're in a situation like this where you lose your existing questions, answers, and reputation for switching IDs.