Instant Search

Google just launched a new form of Instant search. I have a couple of questions for the academic people or maths lovers:

1. Estimate what is the percentage of your query log that can you cover with say X millions queries. Say that this is p%;
2. Estimate what is the average lenght of a query;
3. Evaluate whether would be better to leverage traditional inverted lists or tries;
4. Estimate the impact of caching and your communication framework;

Use all those elements and create your own Instant search recipe. What is the amount of space you need?