A different North American perspective...
It seems very strange that so much angst is being generated about speculation as to what will happen when you spend BA miles to fly non-BA routes.
It seems to me that IF these changes occur, they are really just correcting a pricing anomaly; if it costs 100K miles RT to fly JFK-EZE on AA or on LAN using AA miles, why should it cost less to use BA miles to fly AA or LAN on that same route, when they are all One World partners? Sure, I used BA miles for that route several times, but it was always with the expectation that someday they would realize it was underpriced, so it is hard to get upset that they are 'correcting' the price.
And with what has been announced so far, using BA miles to fly on BA, only 3% of flights will rise in cost, and far greater number of routes will decrease in price. It is hard to claim that the miles are being massively devalued, and ludicrous to threaten class action lawsuits (unless you happen to be a class action lawyer looking to rake in some bucks!) And threatening to quit using your Chase Visa? Does BA really care about a relatively small number of people who aren't really loyal to BA, just using the miles because they got them so easily? Should they? Of course I participated in that promotion, because it was a great deal, but the T&Cs are very clear that the rules of the program can change anytime.. But after all, this is a FREQUENT FLYER program, and it really is appropriate for it to reward people who fly BA frequently!
Personally, I'm surprised that people are allowed to participate in more than one OneWorld FF program, given the ability to book flights on any OneWorld carrier from any program and given that you get status privileges across the program through OneWorld sapphire, etc.
If the changes announced SO FAR are enough to make people quit the program, then most likely they are not the customers that are important to BA.
Lest people think I am a BA apologist or hopeless optimist, I am extremely concerned that all of these changes are merely a smokescreen for a dramatic decrease in availability of award flights, which is really what should be the focus of attention, as taking away availability is the easiest and least transparent way to devalue the currency. Just one example, but last fall I booked 4 RT CW seats on the MIA-LHR-JNB route, and at this time availability was wide open for almost any T/W/R in the summer; looking at the availability calendar now, there is only 1 day all summer I see availability for 4 CW outbound and only 3 dates for return... Looking at some other itineraries, availability is also practically nonexistent.
Whether you think these changes are fabulous, horrendous or insignificant is really immaterial if the availability tanks, so maybe we should really focus on that issue, since without availability the cost of a redemption is moot!