jefequeso: Do you trust those accounts? Because I'd be pretty loathe to trust anything I read on the internet, especially considering how vehement some people are about their hatred of Steam.
That's always the question. Nobody really knows. The accounts could be true. Or they could be half-true considering that actual offenders are likely to downplay their offense and exaggerate any perceived wrongdoings of other parties. The accounts could also be planted by hired detractors to damage Steam's reputation (such practices exist, video game marketing has become a very dirty affair over the last two decades).
But no matter what you think about the reliability of these reports - one sad, simple, and objectively verifiable truth is that Steam _does_ reserve the right to do such things through its license. Even if you don't believe that they're exercising this right right now, you should be aware that you in fact did (by agreeing to the license) give Steam the power to take your purchased games away from you whenever it pleases them.
There is no need for such a provision in the Steam license. In fact, the Steam license could easily be much, much more customer friendly. But most customers don't seem to care, so Steam takes as many rights away rom the customers as it can get away with. Origin does the same, the only difference is that Origin is worse at determining what it can still get away with.