It's arguable that queries like [southwest airlines] are even a search. The vast majority of instances are probably URL-illiterate users merely trying to get to Southwest Airlines' web site. (And Google must know rather precisely just how many.) For these users, search is really operating as a natural-language alternative to DNS so such a clickable banner will help them get there.
More than just advertising, this represents an element of curation on such search terms, to get you to the place you're really looking for. It'll help avoid situations like when that one blog post appeared at the top for [facebook login] and suddenly bunches of users couldn't find Facebook.
Like any technological tool, it could be misused for evil, and so will require vigilance in the court of public opinion if not in actual courts.
(Disclaimer: I'm a potential Googler, currently in the interview pipeline, but these views are my own.)