Nice arcile Brien.

There is also one other thing that a "good" Search Engine needs (IMHO).  That is the vision to deliver excellent search results.  Which is why Google has so far out searched the others.  Yahoo! and Live are playing catch up after having neglected their search platfrom for a number of reasons.  Ask has tried to have that vision but doesn't necessarily execute it on it all that well (just look at how slow their crawl rates still are).

Google has excelled at search because that was it's focus.  I wonder how Google will continue to excel with their diluted focus and an apparent desire to dominate in many, many non-serach related markets.  Time will tell.