DVD rent-by-mail outfit Netflix ( NFLX) was battening down the hatches Tuesday following word that Wal-Mart ( WMT) is preparing to kill its category. The company, which shot up last night after it affirmed earnings estimates, was falling back in the premarket session after Wal-Mart lowered its monthly DVD subscription fee to $15.54 from $18.86. The price covers renters taking out two disks at a time. After going as high as $25 last night, Netflix shares last crossed on Island at $22.90, down 10 cents from the 4 p.m. EDT close. Blockbuster ( BBI) could also feel pressure on the news, though its shares hadn't done any premarket volume. Monday night, Netflix said it expects to earn $3 million to $4 million, using standard accounting, for the second quarter ending June 30. It alsoexpects revenue of $62 million to $64 million, compared with its prior forecast of $60 million to $64 million.