Is having the password visible in the page source a security threat?

Hi Folks,

I posted a thread earlier about how to force a text box in password mode to keep its user input after a post-back... http://forums.asp.net/t/1336216.aspx

Someone, came with the suggestion of using,
Me.txtPass.Attributes.Add("value", Me.txtPassword.text))
to reassign the password value to the textbox...

This method does indeed work, but it was mentioned that then the password value would be visible in the page source...

t's unclear to me if having the password visible in the page source, is actually a security threat or not...
I would assume, that the only person who could view the page source at that time, would be the person inputting the password...so there would be no actual ?threat'....

Are there ways in which this password in the source, could be seen by someone else then the person who did the inputing?
(The pa ...