Checking up on people's work is so time consuming as to make it economically unviable -- therefore you must work with people you can trust.
I've hired a bunch of folks through Ash's company, OrganicApex. Six of them are link builders, i.e. the kind of folks that do a lot of directory submissions.
OA finds, interviews, hires, trains, and manages these people. They all work in one of OA's offices, but they work for me. The system is working really well.