Factcheck.org, the Washington Monthly, and ABC News all fact-check Mitt Romney's claim to have created 100,000 jobs, including 90,000 at the office supply chain Staples, and none find it particularly credible. The Washington Post, which calls the claim "untenable," notes, "Left unsaid, of course, is all the jobs that might have been lost at small stationery stores unable to compete with the low prices of Staples, Office Depot and so forth."
Of course the difficulty of competing is not just on price — my local office supply store now has lower prices on many items than my local Staples does, which may be why the local business is one of the rare such stores that has managed to survive and thrive. It also has to do with marketing spending, inventory, speed of delivery, and the online part of the business. But the point is the same — those 90,000 jobs weren't just created out of thin air.