Federated search: nice to have or must have?

That is the question:  Is federated search a “nice-to-have” or is it a “must-have?”
When I first joined Deep Web Technologies in September 2008, I first thought the former:  That federated search is a nice-to-have, reflecting on my general ignorance of the power of federated search.  I thought it amusing, given my 20+ years in information [...]