It doesn't cost nothing - it costs time and convenience to create different accounts and log in to them all separately when you want to change which account you are using.

I searched through the User Agreement. I think you're correct in that this is not specifically prohibited. Similarly, using multiple accounts to purchase multiple copies of the same game and multibox is not specifically prohibited (to my knowledge).

If you are the kind of person that would actually want to play different games at the same time, it does make sense. However, I cannot think of a legitimate reason to actually want to play multiple different Steam games at once. I have a hard enough time being good at any 1 game I'm playing.

Should you be doing this? In my opinion, no. I use the community-oriented features of Steam all the time and the Cons you list would affect me greatly. Having multiple accounts would be a tremendous inconvenience for me, and I don't care about any of the Pros you list.

Exceptions: There may be some games where it would make sense to have a separate account for just that game. I hear you do a lot of sitting around in games like Eve Online; perhaps you would want to play Bejeweled while you wait for something to happen?

Because of the way that steam does things it's not able to have multiple auto sign in configurations per installation. You'll have to resort to trickery:

• Disable account credential saving in the settings dialog.
• Create a shortcut for Steam on each windows account, edit the properties and give it these launch options -login %u %p. This logs into Steam with the specified Username and Password combination. Replace %u with the username, and %p with the password you want to login with (Steam must be off for this to work).

Source.

If you still want Steam to automatically startup, while logging in to the appropriate account, disable automatic startup within Steam and place the shortcuts in the Start menu → Programs → Startup folders of each windows account.