Business & farm

This is from the W-9 form instructions here ... if you are a sole prop and do not wish to give out your SS# you can use the EIN ... this is one of the best reasons for getting an EIN even if you are not required to do so.  I have been in the business almost 30 years and have never had an issue with this and neither have my partners some of whom have been in the business more than 50 years.  

Part I. Taxpayer Identification Number (TIN)
Enter your TIN in the appropriate box. If you are a resident alien and
you do not have and are not eligible to get an SSN, your TIN is your IRS
individual taxpayer identification number (ITIN). Enter it in the social
security number box. If you do not have an ITIN, see How to get a TIN
below.
If you are a sole proprietor and you have an EIN, you may enter either
your SSN or EIN.