Well, life would be pretty boring if everyone held the same views.
Agreed! It's always good to discuss and very boring if everyone holds exactly the same opinion on each topic.
I'm not condoning people buying a clearly cheaper ticket to try and use as a flexible one either. I'm just aware that there are a whole host of good reasons why you might have been unable to make your original booking. I'd hate to be in that situation and have to throw away a £50 ticket and buy a new one for £90.
Whilst I know exactly what you mean, for the vast majority of people (including those who moan to the Guardian), they will save a lot of money by purchasing Advance tickets on the 9 out of 10 (or whatever) times they actually catch the right train. And then they'll moan like hell because they've had to pay more on the 10th occasion - just because they didn't rearrange their Advance.
Using your figures, you might save £360 on the 9 occasions you use an Advance instead of a walk-up, and then you "lose" £50 on the 10th "throw away" occasion.
Whilst most passengers don't work things out like that, the reality is that buying Advances can be very cost effective EVEN if your plans aren't always 100% reliable. But you have to consider the total spend over time, not just the "rip off" on the one occasion your plans changed.
Passenger Focus will be doing the world of passengers a massive dis-service if they end up in a situation where Advances are in some way a down-payment on a flexible ticket, because it messes up the whole economics of Advances for the TOCs and likely leads to higher Advance fares as a result. Which is good for the moaners, but not good for those who make appropriate use of Advances.
Advances were originally intended, I believe, for those whose travel plans can be shaped to meet the times of least demand on the railway - students, pensioners, etc. Not to give business people who need flexibility, a cheaper way to travel.