I favor using independent accounts, but I never mind using OpenID for insignificant site access, when more sites were implementing it back then (not sure why it isn't used much lately).
Because it never gained traction and Facebook Connect pretty much killed it because it doesn't require setup of an additional service. Mind you, Facebook Connect is a big privacy and security risk, but it's much 'easier' to a user than setting up OpenID, which is why it won.
I only hope Persona takes off, as it's a much better solution.
I think, there're way more disposable email services than non-authenticating OpenID servers.