Blitz is never the same game as standard. You never have time to properly analyze a position, so certain types of moves... specifically moves that are able to gain on the clock for you, are a lot more valuable.
What kind of moves gain time? Attacking moves :) In general it's easier to attack than defend. You can attack on general principal (weak squares, open lines, remove defenders, bring more attackers, that stuff) but to defend you have to calculate, and that takes time. If the attacker is wrong he loses the initiative. If the defender is wrong he loses the game :p
And that's true even when you're just attacking in general, not just the king. So sacrificing for the initiative holds the same kinds of potential time advantages.
So in general I think all good players, not just GMs, play blitz more aggressively than they would a regular tournament game.

Are you more aggressive when playing blitz ?
I watched a few GMs playing bullet and I was suprised to see how aggressive they were. Sacrificing pieces early on, etc. Would it be accurate to say that GMs are more aggresive at blitz than at standard? Or do they play the same game regardless of time controls?