Going under isn't the only concern. A free service which most certainly costs them (bandwidth, power, rackspace, IPs). Even if they're small devices, they add up. And an offering that is losing money will get bumped for an offering that is earning money.
I'm mainly just predicting the future HN post. Panda tears will flow. Just think back to Joyent cutting out the old TextDrive lifetime hosting. People more than likely got their money's worth out of it, but still a large amount of drama.