One volunteer there - was a persnickety old-ish man who was very particular in his tastes. He liked certain brands of bikes, in certain years... and poo-poo'ed everything else. Among his idiosyncrasies, was insisting that every time a tire was installed on a bike, that the logo from the tire match up with the valve stem.
When asked about this - he always replied that installing tires this way just "satisfied his aesthetic standards." To that end, it is a nice way to make everything is nice, and neat - if you think people are paying attention to the alignment of your tire logos... that is ; )
Only recently did I learn that there is another incredibly valuable reason for installing the tires on your bicycle this way.
It helps you diagnose flats!
After 3+ years of commuting, I've noticed that the types of flats I get are more of the "slow + annoying" kind and less of the "fast/catastrophic" kind. The latter is often easy to diagnose the cause of the flat, e.g. nail, screw, huge piece of glass, tube explosion, etc.
The former (slow + annoying) can be somewhat difficult. If you find yourself getting flats for no apparent reason, there very well may be something embedded in your tire. A great way to find this out is to examine the tube after you remove it from your tire.
Pump up the tire and see if you can see, feel, or hear air coming out of it. For subtle and tricky flats, submerging the tube in a small basin of water will typically yield the source of the flat. Sometimes it takes a few passes through the water before you see the small bubbles trickling out.
Once you identify the problem in the tube, use your valve as a reference point and find the corresponding place on the tire where you think the origin of the flat is. This is almost impossible if you DON'T match the tire logo up with the valve.
This morning I got a flat, found the whole in the tube, then used the location of the tube to try to identify where the flat was coming from in my tire. It worked like a charm... there was a tiny piece of glass just barely poking through. Because I had the logo matched up with the valve, I was able to track down the source and remove the glass. Because it was so small, it may have been impossible to find the shard of glass by sheer visual examination or carefully running my finger through the inside of the tire.
So the next time you get a flat, line the logo (or writing) of the tire up with the valve. It'll help you prevent future flats by identifying the cause, faster!