With credit card sign up bonuses, promotions, CC bonus categories, etc, it's not too difficult to build up large balances with (most) of those programs. Amex is probably the only one out of that whole list that is hard to build up a large amount of points.

Personally - At the beginning of the year, when I decided to start planning an end-of-year trip, I chose my AA account to use since A) the balance had gotten pretty high, and B) it seemed the most likely of all programs that I had points in to become devalued in one way or another in the short term.

Looking at that decision, I'm happy I made it ... I used those points to book a trip in Etihad Apartments class -- and with all of the married segment silliness going on now, combined with variable-priced awards, it would have been much harder to put that award together today compared to then. The points in other programs (eg: Chase, Cap1, Amex), can still be transferred to many different airlines, and are much lower risk of a similar single-handed move causing such a problem in a good redemption.

It's important to have enough points that allow you to book the kind of trips you want, and it's also important to have it spread around to keep your options flexible.