[ghastmaster]

> Ebay sends these mails asking you to update your personal information in order to 'improve security'.

The question is then, "Does providing updated personal information improve security?"

I can think of a scenario where this would be true. I have an account somewhere that has an email address that is no longer in my possession. By updating my information, my account is more secure. I think it is plausible that updating other information would improve security as well.

[angry_dane]

Well, they are sending this mail to an email you do have control over. Maybe you have another example?

[ghastmaster]

If your phone number needs to be updated and you have not, that would be something that could be used to aid in an attack if the wrong person was now using it. By sending an email, you can become aware of it without being in control of the phone number any longer.