Oddly enough I have had one program that provided an uninstall script that actually left nothing behind, and as a really sharp counterpoint to Steam it was the GameStop digital download service client. Due to my experiences with Steam I went into that uninstall absolutely loaded for bear and expecting hooks everywhere, and there was nothing...no registry entries...just...nothing.
Not wanting to swap advertisemants I won't name the cleaner I use, but I pretty much agree with you.
Back on Steam and Malware though...all programs tend to leave junk behind that didn't make it into the uninstall script for whatever reason. But leaving behind a process that will reinstall the program is pretty poor form normally associated with ad tracking browser toolbars and other lower life forms. At various times Valve has 'forgotten' to include the client update function in their uninstaller, so when I just used the uninstall and figured I'd clean up later since I wanted to play whatever game I just activated it reinstalled the client for me as an 'update'.
------------------------------------------------------------------------------
Moderators please note that I mention removal of the Steam client only in reference to games that use Steam activation DRM and do not require the Steam client to remain on the machine, not in reference to games that have 'Steam checks' requiring the Steam client to remain installed. The Steam client does come with an 'uninstall' feature, however poorly implemented, and nothing in the Steam user agreement suggests that you cannot uninstall the client.
-------------------------------------------------------------------------------
Valve puts hooks in their DRM that force customers of other companies to become Valve users. The hooks do not make the DRM any more effective as DRM or do anything else for the publishers, they just strengthen Valve's market position. Then they blame the publishers when people complain about being forced to use Steam.
They then use the size of their market segment to sell the DRM full of hooks to more publishers. Despite there being DRM available that publishers could use that is just as effective as DRM and doesn't inflict anything else on their customers, which a good publisher would probably prefer, they can't just ignore the fact that Steam is a large distribution point.
The more publishers choose Steam the more customers are dragged into Steam's market base whether they like it or not. The more that market base grows the more publishers are forced to use Steam distribution. This is a feedback loop that allows Steam to succeed no matter how offensive it is or Valve chooses for it to become in the future.
Get it yet?
The relevance here is that it seems easy to predict Valve's future actions from their past performance. SteamOS is their Linux version. If it becomes at all popular then porting games to Linux platforms becomes more attractive to publishers. Great.
Unfortunately those ports are still going to "require" DRM, and Valve will provide it. Can Valve be expected to include in that DRM the capacity to operate in every possible Linux environment? Or will it be 'tuned' to SteamOS since "that's the Linux environment for gamers anyway"? And if the SteamOS 'just happens' to have marketing tools for Valve's distribution business built into it? No surprise there either, and what a convenient way for the DRM to verify that the OS is a 'suitable' environment. It can just verify that Valve's ad client is installed!
But a Linux environment is user controlled, so you could...oh, wait, I can picture it now...WARNING: modification of the OS may interact poorly with DRM that publishers choose to use on their games. Through no fault of ours you are forced into our customer base and then forced to remain there. Remember, Valve loves you and publishers are evil.