I've been seeing some more Hipmunk ads on Google and they have some billboards on the 101 freeway in the Bay Area. Unfortunately, air search is a low margin bu

I've been seeing some more Hipmunk ads on Google and they have some billboards on the 101 freeway in the Bay Area. Unfortunately, air search is a low margin business so it's hard to get aggressive on advertising and expect to break even w/o the ability to upsell to packages like the online travel agencies do.