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That could mean that people that btob buyers are seriously looking for services may often go to google for the express purpose, rather than "stumbling over them" in MSN, Y! AV etc etc. Business professionals seem to be more targeted than general consumers and want to get results fast (thats their job), so they probably appeciate having the commercial and info results separated and will look straight to the right in Google. They dont want to waste their time shuffling through info sites, (they probably already know their industry anyway), to find the buy button.
That said its a great point that otehrs have made that it depends on the sector. Do what we do and use both! For Europe i hear (only from here) that another PPC is worth a try too (cant remember the name).
Our observations indicate to us that Google seems to have liked the word "free" alot when indexing new URLs. It seems to also like web sites that are intensly informational (the phrase "help" comes to mind).
We don't know if Google weights certain keyphrases higher than others when scoring URL's. It could be our imagination or other reasons giving us the impression.