I should have put more info in my post. In fairness to Avis, my "downgrade" was on a one-way rental from SFO to Palo Alto. But I've done that several times before and never had that problem.

Recent rental at the Palo Alto location:
reserved: full-size
received: Jeep Liberty

which I don't much care for. Drives like, well, a truck. I guess it is a truck, so I should have expected as much.

And by the way, I liked the Alero. Relative to the other cars in the fleet during that era, better than the Chevy <something>, the Lumina, the Monte Carlo. In fact I had the Monte Carlo only once and would always insist on something, anything, other than that.