For contractors, that's a big piece of it....normally you as an employee pay 7.5% payroll tax for FICA, SS, etc. and your employer pays the other 7.5%. So there's that piece and then there's the issue of paying it quarterly (doesn't change the amount, but does add complications).
My DH owns a business, but it's a C-corp with institutional investors and he really only owns about 30% of it...the company obviously deals with tax issues (although they're not profitable yet, so not much tax to be paid), but in addition to being an owner, he's a paid employee and that's just like being an employee anywhere.