When we were in Mexico, there were military checkpoints out on the highway (no joke) with INTENSE speedbumps so you had to slow down. Every cab driver I saw would put their flashers on as soon as they started slowing down. Seems like a pretty good idea. I definitely don't see how it could hurt.
Sometimes I see Mustangs with the oscillating lights... I think that's a great idea too. Only works for turn signals though.
I'm FOR that. I actually had never considered my hazards, but I ALWAYS give brake pulses to try and warn the traffic behind me as I'm coming to a stop and while stopped. The last thing I want is someone plowing into the back of me at highway speed.
I pump the brakes too. I did consider that if I'm reaching forward to turn the hazards on, I am a little bit closer to the airbag. Not really something I want.