The In-N-Out people insist that it is, and they've filed suit against Grab-N-Go Burger, an independent restaurant in Aberdeen, Maryland. Besides the name, Irvine-based In-N-Out says that the Grab-N-Go color scheme too closely resembles In-N-Out's (never mind that In-N-Outs are nowhere near the Grab-N-Go). From the OC Weekly:
This isn't the first time In-N-Out has gone after alleged copycats. Two years ago they were victorious in a trademark infringement lawsuit they filed against one Nicky's In-N-Out in Illinois. In 2007 they took a Utah-based burger joint called Chadder's which offered "Double Doubles" to court and won.