[pbhjpbhj]

It's unauthorised access to the computer.

As I understand that's unlawful in USA and UK at least.

[pjc50]

The authorization will have been when you agreed to the EULA. Or at least that's how the argument will proceed in court.

[pbhjpbhj]

If it's in the EULA? I didn't check, though it crossed my mind, fixing a tap [faucet] instead.

http://pastebin.com/PTG57bXb is the .deb and the online "Steam Agreement" - section 2A of the later is probably most relevant from a brief look through (unless they've hidden things under non-relevant headings). That requires you to give them rights to run "the software".

There are parts about their rights to your UGC, but that doesn't seem pertinent really.

Nothing seems to be a warranty from you as user to Valve giving them rights to snoop around your system and upload data they find.

[Zikes]

Likely runs afoul of CFAA in the US, but only because of how vague the law is.