I purchase a lot of last-minute, one-way tickets. Now, when I say "last minute" I really mean it--- of the 6 one-way tickets I've bought in the last few months, all 6 of them were purchased from inside the secure area, all results of diverted or cancelled flights, I'm stranded somewhere between home and my client and "I absolutely positively gotta be there overnight." I've had the SSSS on my boarding pass on all of them.
Fortunately, since I was booking these from INSIDE the secure area, I could use kiosk check-in from the pier/terminal and not have to go back through security.
I don't get the same SSSS-action on my last minute, round trip fares, though.