Does everyone who marks Individual/Sole proprietor on their W-9 get a 1099-M sent to them if over $600? If not, what is the best way to determine who gets one and who doesn't?

Thanks!

In general, all individuals and partnerships (not corporations) get a 1099-MISC for non-employee compensation. But the more specific rules are here:

http://www.irs.gov/pub/irs-pdf/i1099msc_07.pdf