My most recent episode was at the 9000 foot visitor station on Mauna Kea. The folks there said that I shouldn't attempt to drive up to the telescopes without a 4-wheel-drive vehicle. So, I went in the parking lot and accosted occupants of the first 4-wheel-drive vehicle that came by. The driver of said vehicle had seen me lecture in San Francisco. I got my ride.
Just by standing at that 9000 foot visitor station, I'd passed through the nerd filter.
Then, a few weeks ago, I happened to come upon a local radio club's ham radio field day operation while hiking in the woods with my wife. An co-worker from 10 years ago walked up. It turned out he'd just gotten his ham license.
This stuff happens all of the time. Of course it helps that I am somewhat recognizable in tech circles, so people who know of me tend to walk up, but on the other hand I am not that well known.
What are your experiences beyond the nerd filter?