Only recently I've come across a couple of situation were I have attached my Lapel mic (with Sennheiser G3 system) to a presenter positioned pointing up. They have mentioned that they usually have it pointing down or have had in the past. I then noticed it on the Olympic coverage that the presenters then had theirs pointing down. What the logic behind this?
It keeps the plosive mouth sounds and breath rush from hitting the mic. lavs are almost always omnis, so they don't care where they are facing too much, you lose only a little volume if you point it down, but you won't hear the wind blowing out of the talent's nostrils any more either. I first saw BBC guys doing this, and I figure if anybody knows audio, it is the BBC.