Shares of the 3D printer makers fell after an anonymous contributor on the website Seeking Alpha wrote about the rapid run-up in 3D Systems (DDD) shares. The author said it was reminiscent of the dot-com boom of the '90s. 3D shares fell 13.9%. Stratasys (SSYS) shares fell 9.9%. ExOne Co., a rival printer company, filed an amended registration with the SEC for its IPO. It plans to sell 5 mil shares and sees an offering price of $14-$16 per share and plans to list on the Nasdaq under the ticker XONE.