In some ways, it would make sense to break up Yahoo!
The fact that Yahoo! owns the search technology doesn't really come through in the way Yahoo! sells it's inventory. There are definite disconnects in the different arms of its business.
We buy from different representatives for search, display and Kelkoo. The 'wonders' of Yahoo! (in my opinion) are not effectively pushed by the staff. Where's the advertising on Del.icio.us? Where's people pushing ads on Flickr?
In my opinion, Yahoo! long ago passed the point where it could easily grow organically. The rash of acquisitions it has been engaged in show that the management are aware of this.
We are still awaiting the next update to their search interface. They are about to start pushing a rival to YouTube, hoping to be able to use the Yahoo brand to recruit large numbers of people to the site. All this requires money and has no clear advantage to the company.
Risks require a good chance of return at the end of the process, I don't believe Yahoo! are leading the way in this.
To be fair to them though, they still own a couple of VERY large golden geese. Yahoo mail is definitely one, and the Yahoo portal will has one of the highest reaches of any internet area in the UK. They're not going to be gone any time soon (though someone else might own them!)