Haven't tried any 0.5x but am about to pay the phone bill.
And that too has posted as 2x rather than the 0.5x.
I am not going to get too excited about this, the odds are squarely on this being a mistake, not an unpublished promotion, and quite likely that the extra points will be reversed in time - especially if large numbers become involved because of eager members looking to maximise points. However, statement cycle just closed, so it is a brand new month, and I think I may chase up a few bills that wouldn't normally be paid until later in the month, and pay them now. Worst case, I am no worse off when the points are eventually corrected, best case, and the extras remain.
The cynic in me wonders if this may not be a gambit by Amex to increase billing in this financial year.
1. Make a "mistake" and award 2x points for everything.
2. Don't publish anything (it is after all, a "mistake")
3. Wait for the word to spread like wild fire on boards like this (they have seen this before, remember 10 trans for 10,000 points)
4. Watch the over enthusiastic make large charges that they otherwise would not (some may be tempted to pre-pay tax this year, rather than waiting).
5. Correct the "mistake" by reversing the incorrect points
6. Calculate any "cost" of extra points which have been transferred / redeemed (and how long it will take for the negative points balance to be recouped, less any card members who close their accounts - noting that these members are probably points "exploiters" anyway, and not the profitable sheep they want).