Alan Bleiweiss: If it`s a site with local visibility needs, yes - this is a known factor as part of the NAP (Business Name, Address, Phone) consistency scenario. As far as sites that don`t need local, this is a fascinating question I`d love to see data on.
Tim Capper: Most certainly >> but in what circumstance.
If it is ecomm, 100% yes, and its pretty much a legal requirement to have contact details in at least the T&C section of an ecomm site.
If you are not ecomm, then what business would not provide a number ?
If it was a random blog, not a problem
It will certainly depend on circumstance
Will Google trust a site with a phone number on it more then a site without one? 
