So basically Steam is fine, has been for 20 years, and has competitors waiting to step in and take over the market if Gaben and co ever succumb to the temptation to cash in for a quick boost to corporate profits for a few years at the expense of ruining the business forever after, as impatient shareholders might demand if it were a public company, which it isn't.
It's true though, it could fall apart at any moment. So could anything. I expect piracy will be the big winner when it happens.