Amazon has pulled Macmillian's books from the Kindle store in a protest over pricing that could signal a conflict with Apple, a source said late Friday. An insider claims that Macmillan had asked Amazon to raise prices from $10 to $15 and, as a pressure tactic, Amazon is temporarily denying sales. The NYT contact doesn't say how close Amazon and Macmillan are to clearing the impasse and which side has the upper hand.