One thing that i don't see much coverage over is how non-technical users get the power afforded by advanced querying. Something that drive me to create something LIKE http://weblivz.com/ was through my experiences with querying in a project which involved many hundreds of millions of distributed records.
In that project we had a team over over 20 experts writing specific queries that were semantically relevant to the area they were in and the output of one search was actually a fairly complex backend query most of the time consisting of the union of multiple backend queries all reformatted for a specific output.
Today many sites - and emerging distributed query sites - are focused on simple queries, but this requires that you KNOW semantically what to look for and that you want to type it in all the time. In addition it assumes you know how to construct fairly complex (it's all relevant) queries.
So, YES, we need all these cool sites that do the keyword searching. But we ALSO need something a bit higher level. We need to hide the user from the complexity of searching and also make it easier for them to remember the kinds of searches they either constructed or used before.