Sex Selection in the News

Need more evidence that sex-selective abortion in the US is going to be a major topic of discussion? <a href="http://www.worldmag.com/2012/09/boy_crazy">This article</a> suggests that, because sex-selective abortion is illegal in many other countries, many wealthy would-be parents are travelling to the US for sex-selection services. Notice at the end of the article where Dr. Steinberg draws the line. Does this make sense? Is there any ethical reason to consider sex-selection to be morally acceptable but selection based on these characteristics to be immoral?