If the gift is considered to be one-half from each spouse and only one spouse files a return, then that would be an issue the non-filing spouse would have to address (if that ever arises).
Note that the penalty for not filing a gift tax return is typically based on gift tax due. In most instances no gift tax is due and, thus, there is no amount on which to base a penalty. The only possibility left would be a flat charge for not filing a return (typically in the neighborhood of $435).
