That's crazy that I never heard about it. Is it a recent thing? Very cool that it has taken off regardless, and I suppose serves as a proof of concept for Lyft/Uber.
Not recent at all; Wikipedia says it started in the DC area in 1975, and I definitely remember people using it when I was a kid, which would have been early '90s. http://en.wikipedia.org/wiki/Slugging
It's more popular in certain geographic and industry pockets. I used to see long lines at the Pentagon and Crystal City for slug riders every afternoon/evening.
Yeah, it's definitely confined to certain demographics. It's especially popular among government/defense types in Virginia. There are a couple of benefits that make it popular with them -- namely that it's free and the system is primarily designed to take you to the far-flung suburbs (where the cheap housing and good schools are).
Given that, I doubt Lyft (marketed towards urban millennials who have smartphones and are cool with riding around in cars with mustaches) and Slugging (mostly used by staid, middle-aged, middle-income workers) are going to compete with each other.
(Still kicking myself for not finishing that app for Slugline-like ridesharing 6 or so years ago :) )