** Hydrogen fuel cell maker's shares reverse course, fall as much 7.6 pct to $2.08 in heavy trading after market opening
** Shares are now down 4 pct at $2.16; PLUG's shares were up 7.6 pct at $2.42 in premarket
** Under deal signed with Amazon.com Inc on Wednesday, co will subsidize Amazon's product and service commitments by issuing up to 55.3 mln warrants to purchase PLUG common stock
** "We have concerns about PLUG subsidizing a relatively new customer while others have done the missionary work" - Roth Capital Partners
** PLUG's existing customers could be expected to pursue other sources for forklift fuel cell systems such as Ballard Power Systems and Hydrogenics Corp ; Shares of BLDP were up 3.7 pct at $2.47 in morning trade
** More than 19 mln shares traded, nearly twice their 25-day moving avg.
** Up to Wednesday's close of $2.25, stock had gained nearly 88 pct YTD