It is not clear to me when I have to require a W-9. It seems clear when I use services preformed by an individual or business, but do I have to require one for every single payee?

Eg.

Phone service (ej: Bellsouth)
Freight (Fedex)
Supplier of Goods purchased for resale
Good consumed (eg Home Depot; Office Depot; etc... )

What draws the line between whom must send me one or not?

Thanks!