Ask HN: Managing email address and username changes across many, many sites?

PG wrote recently that to "replace email" would be a great startup idea. He noted that there should be a "todo list protocol", but I have another sore spot for you and PG related to email:

I am changing jobs and I have no clue how many websites I registered with using my work email address. I have tried to manage the important ones, but I'm going to lose notifications for bugs I submitted, and other notifications or access to various projects. I wanted to keep work and home/other email separate and I have never worked anywhere where I did so much open source work, etc. that I want to continue after I left.

For those that had this problem and did something about it to avoid pain from future changes, how do you do it? Is there a "Gravitar" for email addresses? How about usernames? I've had to setup new accounts in places because the old username was too tied to work identity.

It may seem at first that the easiest thing to do would have been to have used personal email for everything and my work email for nothing, but that has it's problems, too.