I ashamedly use Strava. Yes it has been motivating me to ride harder, but still not to become a jerk passing people. For the last five years I have been barely pushing the pedals, going for the inverse of Greg Lemond’s famous quotes, I was making it easier, so I was getting slower.
One thing to remember about Strava results, some smart phones (iPhones especially) are a little loose on how they calculate location. Often smart phones calculate their location by using signals from cell phone towers and not the GPS satellites. This reduces the load on the processor, and thereby extend battery life, and allows a much quicker initial location calculation.
For all you know, the local KOM’s iPhone could have calculated him as crossing a segment’s starting line 20 feet after he really did. May not sounds like a lot, but so many segments are so short it could end up make the difference.
I ran both my iPhone 4 and Garmin Oregon 300 at the same time this weekend at Fountainhead. Made a 13 second difference on a segment for me. On the third loop, the iPhone showed my time as 24:57 (88th/446), the GPS 25:43 (106th/446).
I also made this visual comparison of tracks up near Patapsco.
from this ride: