Agree with the OP on both angles - I think Steam and Impulse are VERY important for several reasons:
1: Platforms that are as easy - or easiter - to use as the premier game distribution platform, The Pirate Bay.
2: Game distribution the way it should be - updated in the background, always up-to-date, no hassles, no DVD that must be in the drive, and unnoticeable CD-keys.
3: Portable game library. Install steam/impulse, download, done. Anywhere, any time. New PC, old, holiday, no problem.
And with that said, Steam has a too prominent position. There is no practical reason that I can see for them to sell games at MORE than retail box prices. Or even on par with them. (That goes for Impulse too, but at least here, their prices tend to be lower. Tend to. Not always.
That sales pay is no surprise at all, why do you think retail shops has had sales since forever? 
As for Defcon, it's a cool game. Take a look. "The world's first genocide-'em-up.'. Unless that's changed, the single player (demo) version is free.
http://www.introversion.co.uk/defcon/
The sound is pretty brilliant. It starts off peaceful-like, but as you get nuked more and more into oblivion you start hearing wailing parents, desperate crying, and so on. Pretty depressing in a way, but very well done.
As for the game that got 36000% increase, it is, of course, NOT a well known game. It's a game that sold nada before - probably indie - and with the sale it got both publicity and came down to a reasonable sale. Tank Universe or something, I'd guess. (Good game, too, btw.).