Have been with Citibank for almost 9 years, just realized that they're charging annual fees for me again after waiving it since the beginning. I guess I'll have to call them...

I'm sure there's some formula involved based on your annual income + previous spending + credit history + .... I'm also quite sure there's a rough estimate of how large your total credit limit should be across all banks.

I have personally never asked for a single credit limit increase from Maybank or Citibank, but they've continuously increased it over the years to some scary figure...

I completely agree. Make sure you vote with your money ie. drop Citibank if they're not willing to waive annual fee.

Also leave a polite and professional note on their Facebook page or something to make sure they know they're losing a customer.

I've been lucky that they've waived their annual fee for me so far but I don't have a cashback card.