If they suddenly announced it had gone gold and was available on steam i think steam would ground to a halt with all the people downloading 1.2gb each off it (i assume 2 cds worth).
I would imagine the entire internet will grind to a halt if HL2 is up online. Once Steam has it, someone will post it to the warez channels (even though they're steam files) and set about cracking it...
Thought for the day: Remember the quake "shareware" cd and how quickly it was cracked? Any bets for how long it will take to crack Steam files to allow offline play?
Supporter of the "A happy fredster is a muted fredster" fanclub.