The FAA has published a draft advisory circular entitled "Guidelines for the Certification, Airworthiness, and Operational Use of Electronic Flight Bags (EFB)", that could eliminate portable navigators and chart readers as we know them for aviation, including Part 91 operations.
Robert Goyer covers the issue in his recent article in Flying Magazine. In the article, Goyer points out that the draft AC "strongly suggests that own-ship position (showing the little airplane on the moving map or chart) is an illegal function" and that the "FAA seems to be calling for individual approval of every portable device that goes in the cockpit, something that would cost individual operators thousands of dollars apiece".
Both Aircraft Owners and Pilots Association (AOPA) and General Aviation Manufacturers Association (GAMA) responded to the FAA saying, "AOPA/GAMA believes that electronic flight bag technology will be a critical tool to enable many expected NextGen capabilities at an affordable cost however, this proposed guidance material will limit much of that potential because of short-sited perspective."
FlightPrep agrees with AOPA, GAMA and Flying Magazine, and hopes that the FAA will revise the advisory circular and re-post it for public comment again. We'll keep following the issue and post any updates as they develop.