The problems with this type of software:
1) Technical faults (this is when your clock gets mis-set once, or something, and the expiration system expires your totally valid software.)
2) Forced upgrades. These subscription models almost always seem to be tied into keeping the software up to date. If you don't like some new change, or there's an incompatibility with a new release, you're probably SOL.
2.5) Forced upgrades again -- some people just buy a version of some software, it works great, so their costs after that are $0. But with this model you have to pay either way.
3) What if they go out of business? In some cases the company has sent a perpetual license code to their current customers, but other times they've just found out their software will irrevocably drop dead in x time.
4) The "far future". A few have already alluded to this, what does someone do with a copy of this software 20 or 30 years from now?
"I really do worry about how our future generations are going to handle the fact that a larger and larger part of our common culture is being programmed to self destruct after a limited time."
I have to be honest, I haven't seen this. I avoid DRM-infected audio and video, and for Linux there's vanishingly few pieces of software with an expiration.
"Protesting is what you do when the other guy really has no reason to listen to you. Switch to a different IDE or editor. "
People protest whether "the other guy" has a reason to listen or not. To me, it sounds like JetBrains *IS* listening. But there has not been enough time yet to find out if JetBrains will have a useful response, or just make an excuse why they're going subscription. Plus, of course, people currently have a fully purchased copy of IntelliJ IDEA or whichever IDE, so they don't really need to switch in the coming weeks.