Most of the time transfer of viruses or bacteria occurs via hand to hand contact or touching things that other people have touched. I am more concerned about where a person's hand has just been than I am about the plume.
Ever see someone in a doctor's office cover their mouth (as they should) with their hand and then pick up the magazine they were reading? I never touch the magazines in a doctor's office and the last thing I do on the way out the door is take advantage of the hand sanitizer they provide.
So yes, hand sanitizers do have tremendous benefit.