Amazon.com is in talks to buy online luxury retailer Net-a-porter in what could be the biggest acquisition yet for the e-commerce giant, but the negotiations are in early stages and could fall apart, Forbes reported, citing a person familiar with the matter. The potential deal, first reported by Women's Wear Daily, could value Net-a-Porter lower than the valuation of 2 billion euros reported by the fashion industry trade journal, Forbes said, citing the person.