I think maybe so.
Beer has been made for thousands of years without those modern airlocks and still is by many commercial and homebrewers. I usually just use a piece of plastic film or inverted plastic cup over my better bottles and have never had any problem.
Read this:
http://www.brewery.org/library/OpenFerm.html
and this about Pasteur's famous experiment:
http://science.howstuffworks.com/innovation/scientific-experiments/scientific-method5.htm
That's a more detailed post than most, but it only helps convince me that I'm not missing anything.
I'll grant you that a dry airlock of either common variety is effective at keeping out harmful microorganisms over a short period of time, but that's about all it does. Most of use demand a bit more out of our airlocks, so to say they "work fine dry" is at best a gross overgeneralization based off a limited intended use. I like my airlocks to, amongst other things, prevent fruit flies from getting in my saisons in the summer, slow the ingress of oxygen when aging a bigger beer, and so on. In short, I expect my airlock to function
as an airlock, which it does not do when dry.
I'm not sure how ancient techniques of brewing and open fermentation are relevant to the discussion, either. Open fermentation is best done with certain strains of yeast and has its own set of techniques. Kräusen is often skimmed during the height of fermentation, beer is generally racked and sealed (from air) once it's fallen, etc. Most of us either don't know or don't generally practice those techniques. The same goes with ancient brewing methods. What we know of older beer (and here I'm talking over 100-200 years old, yet not too far back) is that wild yeast and other "infections" were common in aged beers. If we don't want beers like that, or don't know the techniques of the time to prevent such events, then we'd better use airlocks.
So while I appreciate your thoughtful reply, I suggest you're very wrong when you say airlocks function just fine when dry. I'm not saying you need to use them to make great beer, but as a suggestion to a new brewer to not bother filling their airlocks with water, it's a terrible idea. The techniques you're suggesting work very well for those that learn and practice them effectively (and badly for those who don't, I'll point out), but assuming that others do as a matter of course only inhibits helpful dialog and advice giving.
