You can learn a lot by scanning configuration, registry files, and so forth; many have made off with a successful bounty. Most recently, some Steam Beta users dug around in their user interface (UI) files to notice a few interesting lines, instructing the user that the title they are attempting to launch will kick off a friend it is currently being shared with.
"SteamUI_JoinDialog_SharedLicense_Title" "Shared game library"
"SteamUI_JoinDialog_SharedLicenseLocked_OwnerText" "Just so you know, your games are currently in use by %borrower%. Playing now will send %borrower% a notice that it's time to quit."
"SteamUI_JoinDialog_SharedLicenseLocked_BorrowerText" "This shared game is currently unavailable. Please try against later or buy this game for your own library."
Sure, this whole game DRM issue has been flipping some tables around the industry. Microsoft tried permitting users share games with their family, utilizing about the worst possible PR, and eventually needed to undo that decision. Users would like flexible licensing schemes, but the content industry (including the platform owners like Microsoft, Nintendo, and Sony, who receive license fees from game sales) are unwilling to cooperate unless they are assured that users are honest.
Of course, what usually happens is honest users get crapped on and pirates enjoy a better experience, after initial setup.
While there is not much difference, from a high level view, between Steam and the proposed Xbox One, there are a number of differences. The obvious difference is Steam's offline mode, but probably the larger reason is trust. Valve has demonstrated a lot of good faith to their customers; where Microsoft shuts down access to content people paid for, Valve has shown they have intentions for both long-term support and consideration for the user's experience.
Ultimately, I feel as if DRM is not a necessary evil, but while it exists at least there are companies such as Valve who earn trust and use DRM both for and against users. I expect that some day, the industry will turn against DRM either willingly, by legal intervention, or because companies like cdp.pl will use DRM-free as a promotional tool and nibble their way to dominance.
And yes, despite the fact that this will be confused with bias: if you prove that you are untrustworthy before, you will get away with less later regardless of your intentions.