I'm gonna have to stick up for AmEx. It's self-preservation. With lots of people declaring BK and unable to pay off the balances they're running up, I'm sure AmEx is just trying to protect itself.
Liz -- what was your CLI before and after the decrease? I suspect that they're re-evaluating bloated CLs in attempt to reign in risk. That's not to offend you, just look at that recent post on people whose CLs exceeded their income...some by as much as 50%!
I'm just playing devil's advocate here though, so feel free to hate on me. 