In 2009, I had 0 out of 4 certs collected (2 SEA-OAK and 2 SEA-ATL). I guess I kinda understand not collecting them on a flight that goes out with empty seats in F (the two OAK flights), but I was surprised about ATL.
I was never tempted to re-use the certs. Just not my style! I don't mind them going to e-certs as personally I hated storing them and remembering to take them when I needed to.
Dave