Regarding the talk about favicons in the taskbar and window titles: yes, we should absolutely have that! I'm also interestested in seeing the icon everywhere where bookmarks or URLs are displayed, this means e.g. in the bookmarks menu and sidebar and in the history. I think this is not a hard job, just replace the default bookmark icon everytime, with the specific one, if it exists. Regarding the additional problem of different icons for browser, mail, news and adressbook, it simply suggest to use the icons from the status line. I hope you can implement this in a future version.
Favicons for bookmarks could be bug 128457.
*** This bug has been marked as a duplicate of 113574 ***
My suggestion of having favicons almost everywhere seems like a duplicate of 113574, that's right. But my idea of using the icons from bottom left corner of the status line for different window and taskbar icons for browser, mail, news and adressbook is an other issue.