While I agree with the sentiment. Here's why you should not delete your yahoo account. Once you delete your account, yahoo will make it available again to everyone. This means that if you have not unlinked everything it can be used by others to reset accounts on services you forgot that you linked to your yahoo account. Instead of deleting it, forward it all to another account and stop using it. Do not forget to log…
This is an excellent argument for setting up e-mail using your own domain name, though, and for using that for all new accounts and transitioning existing accounts to your new e-mail address as soon as possible. The Internet works just fine when it's decentralised, but particularly with e-mail, relying on the big service providers (or an ISP-provided address, for that matter) immediately locks you into someone else's…
The argument for individual domains suggests itself, or an equivalent follows-the-person mechanism.