Wednesday shares of Amazon.com Inc hit lowest levels since March, slipping 30 cents and moving from $170.25 earlier to closing at $180.21. Mid-October shares were at a record $246.71, 35% up for the year to date. The drop happened on concern that its big spending and aggressive pricing will gain well come holiday season through 2012. After the record October shares, Amazon introduced the Kindle Fire tablet at $199 which was...