http://www.steampowered.com/index.php?area=subscriber_agreementThe highlights (or rather "lowlights") include:
"In the case of a one-time purchase of a product license (e.g., purchase of a single game) from Valve, Valve may choose to terminate or cancel your Subscription in its entirety or may terminate or cancel only a portion of the Subscription (e.g., access to the software via Steam) and Valve may, but is not obligated to, provide access (for a limited period of time) to the download of a stand-alone version of the software and content associated with such one-time purchase."
So, Valve can limit or terminate completely your ability to play Half-Life 2 at any time even though you supposedly "bought" it.
"Valve may amend this Agreement at any time in its sole discretion. As a Subscriber, you agree that Valve may amend the terms of this Agreement."
Valve can change Steam and your use of it at any time in any way.
"YOU ACKNOWLEDGE AND AGREE THAT YOUR SOLE AND EXCLUSIVE REMEDY FOR ANY DISPUTE WITH VALVE WITH REGARD TO STEAM OR THE STEAM SOFTWARE IS TO DISCONTINUE USE OF STEAM AND CANCEL YOUR ACCOUNT."
Don't like some change Valve has made to Steam? Tough sh*t! Your only recourse is to cancel your Steam account.
"Valve reserves the right to change our fees or billing methods at any time and Valve will provide notice of any such change in at least thirty (30) days advance."
Valve is free to change its fees for using Steam at any time.
Read it and weep. Then again, since you were dumb enough to subscribe to and use Steam without first reading this, then you deserve what you get.
No game is worth putting up with that sh*t.
This comment was edited on Nov 30, 00:23.