Despite end of the day praise and the acknowledgement that I'd be recommended for the next phase, not to mention a genuine rapport with the devs that sporadically popped in, the four letter firm acquired a software house and froze recruitment a week later.
I spent a day revealing tricks and patterns - something I charge a substantial daily rate - for nothing. But this is ridiculously common: the more effort required to interview the less likely I am to get the job.
Nowadays I'm happy to walk out of bullshit interviews where they ask open ended questions where only their answer is correct.
You get to a certain age/experience where it becomes apparent that a good interview is an informal session where you have a meeting of the minds not an adversarial grilling.