Facebook Offers, a new form of online advertising, may be the closest thing yet to a measurable, ROI-positive ad platform for small retailers. But will it remain that way? If you’re like most small business owners, you need to manage your advertising spending carefully. And if you’re the owner of an online business, you are probably spending the majority of your ad budget where your customer are—online. But how well does online advertising really work for you? Banner ads and blog spons