Interesting, though a bit surprising to me for some reason that at this late date of medical investigation that researchers are only now discovering the active bacteriophage in mucus.

I was told, a couple of years ago, by an octogenarian, that babies pick their nose and eat the mucus because it has anti bacterial properties. Perhaps there could be some research into the longevity of people who have carried on their early predilection?

Wow. This is big in many ways, not the least of which is how science really cannot assume anything that isn't actually backed by methodic investigation. We all assumed we knew what mucus' function was, so we didn't look at it anymore. Oops. This should be headlines in the mainstream news.

That makes one wonder about the use of toothpaste or even worse mouthwash, especially when dealing with gum infections. Are they a case of 'bad' mucus? Is there bad and good mucus?

I've always suspected saliva/mucus had a antibacterial effect. If an animal (most mammals at least) gets a cut or receives some other bleeding wound it will tend to lick it liberally. I'm guessing that that behavior serves several functions, cleaning, maybe increasing blood clotting, and as this study shows it also applies a antibacterial coating. So next time you cut yourself, forget the Neosporin, just spit on it ;-)

I always wondered why mating couples kiss.

We will be answering questions about the work at AskScience on Reddit tomorrow if you guys have questions! http://www.reddit.com/r/askscience/

It seems blowing your nose into a handkerchief not only clogs your sinuses it robs the body of valuable bacteriophage. After nearly 40yrs free of sinus problems I may also be in line for a very long life. I'll let you know in another 40 yrs.

Older people have numerous problems, one very serious one is to produce enough mucus to protect their lungs from infections. This demonstrates the further importance of mucus.
@TJ Lambert: You are the one that is assuming too much here. There is no one method of investigation that will automatically lead to the 'truth'. Numerous investigations do help towards having an answer, but don't think they have stopped looking at it.
We only know how certain we are of an answer or assumption and we come up with experiments that test that answer. There is a hierarchy of answers (with a certainty that comes with each) that we have made. In this example look at the function of mucus.
We have come up with that mucus traps bacteria and viruses. Then we go down in the hierarchy and say that trapped viruses kill bacteria. If we go further go down, we find out that the killed bacteria releases foul odours and cause bad breathe! (made that up for example)
The hypothesis of the anti-bacterial properties of mucus must have made certain people, though they haven't been able to verify that until now.

If you find you can't see the TV too well - or anything else - try this: Liberally lick your fingers then gently rub your closed eyes for a few seconds. Lick your fingers again and notice the wetness of the returned wet finger now seems thick, with mucus. Repeat the process. Things start to look clearer. (Or is it all in my mind?) Might this be how cataracts form - the mucus over the eye, staying put and slowly drying out?