Saying that Amazon won't hurt much could be shortsighted. I can see where Amazon agressively becomes the online sales tool for many small businesses who currently ship through Fedex. Fedex can take orders, collect payment, pickup and deliver all on line sales, and even sales made directly by the seller once they get fully set up with their delivery service. I already see more long-haul trucks with Amazon signage than even a year ago. I don't know when they started using their own drivers/trucks instead of contracting that out, but it is obviously growing fast.
So even though Amazon is a small percent of shippers, it could take many more shippers if Bezos want it. For a small business, having their internet sales, payment collection, and shipping all in one place allowing them a smaller sales force, collections, etc could be a big money saver, especially if Amazon can offer lower shipping rates too. Amazon could do to shippers what Walmart did to small business. One stop shopping is attractive. Amazon is already promoting their web services. Walmart is getting into online sales and fast delivery too. It won't be too long before Walmart starts shipping directly to consumers without the middlemen like UPS and Fedex in select areas to start with.