The "overuse" of annual passes is a major problem for Disney (it's even bigger out at
Disneyland where millions of people live within an hours drive) - Disney had counted on people showing up a few times a year and still spending lots of money per trip. But the more frequent the trips, the less each annual passholder spends per trip. Because of Disney's fixed costs, it's better to for them to have a guest spend $50 on one trip rather than $10 on each of five trips.
This is not to say that annual passholders don't drop a lot of money, but this is Disney - they want even more.
In California it's too the point where many APers don't spend any money at all. Disneyland has replaced the local mall as a gathering place for teenagers, families and other groups. The result has been a crowded park, longer lines at for the attractions and no increase in revenue. It's not uncommon for a SoCal family to pop in for a couple hours on a weekend, ride a favorite ride, watch a show...and then stop at McDonalds on the way home for something to eat.
That's not what Disney demands.
Disneyland has already increased the price of annual passes. Major changes have been rumored, but the company has also become hooked on the initial huge cash infusion they get from new sales and renewals. The trick, the one they haven't figured out yet, is how to keep people buying passes AND force them to spend more money everytime they enter the parks.