Not sarcastic :-). I see one or two almost every day. Their number seems to have been increasing rapidly in recent months, have you visited recently?

It's been about a month. I guess I just missed them.

As a side-note, I love that I can't tell if a comment is true or sarcastic-faux-science-fiction, and it ends up being true. We live in a really cool time.

It might just be where I walk vs where you walk - I usually see them on Shoreline and between Shoreline and Castro, sometimes on El Camino in that span. A few weeks ago I saw one of the slow pod cars holding up a bunch of traffic in he right lane on El Camino because its top speed is too low for the flow there. :-D

I found a YouTube video from someone who seems to have encountered one: https://youtu.be/FKETvrCZhzU

I'm surprised there aren't more videos like this, though.