For months, Amazon has been applying relatively subtle pressure on Hachette an apparent bid to get better pricing on e-books; unnecessary shipping delays and reduced discounts on paper books have been common. Well, it's not subtle any more. The company has started pulling pre-orders for Hachette titles, either listing them as "unavailable" or removing product pages outright. The dispute leaves many caught in the crossfire -- authors lose revenue, while customers have to track down smaller stores that will take advance purchases.Neither side is commenting on this latest incident. However, it's a tactic we've seen before. Amazon pulled Macmillan's books in 2010 after the publisher demanded more favorable pricing from the e-retailer, which frequently sells e-books at below-retail prices in order to drive adoption. The company only acquiesced after Apple launched into the e-book business with a pricing model that gave publishers more clout. The arrangement got Apple and partners into trouble for alleged price fixing, but it also kept Amazon from taking advantage of its e-commerce dominance to squeeze publishers; they could easily find better terms elsewhere. Now that those companies are legally prevented from making such deals, Amazon may have returned to using its market lead as a weapon against book giants that fall out of line.