Harbor Freight, which is a privately held discount tool and equipment retailer, has seen its Black Friday ad first to the Internet for the past few years. That would seem to point to something that has been widely theorized and accepted: Many of these Black Friday ad leaks are perpetrated by the retailers themselves.
Of course, there are exceptions, in which the retailer in question -- generally a larger one -- asks for the ad to be taken down.
Harbor Freight operates a chain of retail stores, as well as a mail-order and eCommerce business. The company has 449 stores in 45 states.
A slideshow of scanned ad images is available here.