As long as business is not going as well as owners want, the same economic problem exists in private software too - in fact, the private companies get acquired all the time too, and they get shut down, causing DOS for many of their clients.
(See for example: https://www.tumblr.com/ourincrediblejourney )
One difference is that closed-source source usually much less efficient; I cannot imagine "100K+" customers from a commercial org with just a single developer. And when there are dozens or hundreds of people involved, it's unlikely that new owners would turn to outright criminal activity like malware; they are much more likely to just shut down.