Nagware

Rather than disabling features or shutting down, the program pops up a dialog at launch, makes you wait through a countdown before the "Continue" button lights up, or writes "unregistered" in the title bar. Everything works; the only thing missing is peace and quiet.

The business model rests entirely on the irritation eventually costing more than the licence. WinRAR is the canonical case: its 40-day trial has, in practice, never ended, and the purchase reminder has become an internet joke in its own right. Legally the nagging changes nothing – use after the trial is still unlicensed, even if nobody ever checks.