What's been observed in a few failures doesn't prove anything except that these failures can occur.
what else do you want 'proven'

The fact that adding a supervisor seems to help may be encouraging, but it is by no means a proven solution to the problem, since the problem itself is not clearly defined.
if you do something that makes the problem go away is that not a 'proven' solution? Yes, if you have a headache it can, in some cases, be fixed with aspirin or surgery and you can, with some justification, state that the aspirin is not the 'proven' solution, but surgery is; however, should that keep you from taking aspirin?

It's too bad none of the chip makers are willing to publish what they know about this. They probably have a large-enough set of statistics, or, at least, SHOULD have, to make it more understandable.
If I tell you that is not safe to drive faster that 38 MPH on route 4711, do I have to tell you why in order to make you not kill yourself?

I've never denied that these events occur. I do have doubts that these all-too-popular solutions touted by the manufacturers' people are the true "fix." For one thing, I believe that there's a larger risk that the FLASH can be corrupted during power-down than during power-up.
Which is EXACTLY why a supervisor is required and a RC reset is not worth $#!^

Clearly, it can also be clobbered by a runaway MCU as well as by defective code. When the power drops, the Vpp charge pump is presumably fully operational. During power-up, all bets are off.

I'm thinking that the negative-going reset on the MAX1232 can serve to gate-off/stop the external oscillator that drives the MCU.
sure it can, but WHY when you have ZERO, NADA, NONE problems when using a proper supervisor.

I'll have to wait for MAX1232 samples to arrive, as Kai has told me that the DS1232's that I have in house are probably rubbish.
An analysis I had to make due to some reset problems led to the following results: ALL supervisor worked with a 100nf decoupling capacitor soldered directly across the chip (actually added on top of the chip) only the MAX and possibly the LT worked satisfactory with a 1" trace to the decoupling cap. Thus I am confident that a lot of 'negative publicity' regarding supervisors have been due to adding the decoupling cap nilly-willy ("where it fit on the board", "I am using protoboards", "I put them in a socket and wire wrap to them"), ...)

All of this implies that, for those using the really cheap MCU's, the reset and oscillator circuitry costs more than the MCU. I don't know how well that will sell.
Well if the purpose of your design is to use a "really cheap MCU" you will take other shortcuts as well. One thing that should not be forgotten is that in substantial volume basically all MCUs are "relly cheap" and so will supervisors be. I is not my job to disclose what you can buy a full-fledged MCU for when you buy 1,000,000 pieces, but it is not much. Since concern for chip price should be ZERO in low volume designs, the curve of HW cost ves importance is basically a straight horizontal line. If you make ten thingise and your development cost is, say, $5000, why should you be concerned about saving $2 in hardware, especially since that 'savings' is likely to make your development cost rise

Erik