The short and sweet of it IMO;
Participation Awards, No. Never. An Award, like Buckles, Trophies & Plaques, should be earned and not easy to get. TJR said it right, Less is More.
Participation Souveneers/Momentos, Yes. The little pins they give out at Bordertown, Eldorado, EoT, WR etc. are great. I think they're perfect little reminders of good times had by all.