Arduino PWM Frequency - Pros and Cons of Modifying
A PWM frequency of 490Hz means a period of approximately 2.041ms. This allows a high period of 2ms, which is the maximum pulse length required by a large number of inexpensive servos. Obviously if your design uses no servos then this is not a consideration.

Timer 0 itself is used for the various Arduino timing functions (delay(), millis(), etc.), so if you change the frequency used for timer 0 then those functions will no longer have accurate results.