I have been doing some work around sizing the "business search"
market.  I have come up with what I think are some pretty decent
estimates for the total number of queries on online search engines
over the next few years, based on research I've examined from JP
Morgan and Goldman Sachs: 171B (2006), 196B (2007), 216B (2008) and
232B (2009).  What I don't have yet is a good way to estimate the
portion of those queries that might be related to "business search." 
Generally speaking, I see business searches as falling into two main
sub-categories: (A) business news and financial information (quotes,
financial statistics), PLUS (B) "business-to-business" (b2b) or
"business or professional research" searches. Searches that would fall
into the (B) sub-category would be any related to an individual's job
or profession.  Examples would include a salesperson in the metals
industry looking to keep up with industry developments, or a CTO
looking into the data storage vendors for his company.

I used two comScore category breakdowns ("financial" and "business
news") to come up with an estimate of around 3.8% for (A), but I can't
find anything from comScore or elsewhere that would help me
approximate a percentage for (B).  Any insight into that would be
greatly appreciated.