How to recover the Yahoo account when I don’t remember the security question

If you have an associated @yahoo.com or @yahoo.co.uk email address and can remember what it is you can go through the password reset process for the mail account, then once signed in on that email account you might get access to the Flickr account.

There's a reset wizard at https://edit.yahoo.com/forgotroot

1. Select "forgot password".
2. Enter ID and capcha.
3. Select "I can't access above email accounts"
4. Answer your secret questions.

From here:

How to recover your Hacked Yahoo! Account:

“To be able to reset your hacked yahoo password just send a mail to Yahoo Security Department – account-security-help@cc.yahoo-inc.com. always remember to be polite in contacting them, tell the whole story, don’t blame them for your hacked account, tell them when is the last time you access your account, supply them the password that you last used to accessed your account, give them all the information you entered when you register your account or just the information when you last update your account.”