Mah is a term used (as far as I know) exclusively by batteries to give an estimate of their capacity. For example a 1000mah battery contains the equivalent amount of energy that a device that draws 1000ma would use in 1 hour. Here's the real kicker, if you actually draw that 1000ma from a 1000mah battery you won't make it the full hour =) Because the AH rating of a battery is generally measured at a fixed current draw that is LOWER than it's total capacity. For example a typical lead acid battery that is rated for 7AH's which is the same as 7000mah rating is based on a 20 hour discharge, which 7/20 = 350ma's for 20 hours. If you draw more than 350ma per hour the capacity will be reduced because more energy will be wasted from heating in the battery itself, mind your during the discharge the voltage will drop so the total power available will gradually decrease as the cell is drained.
Find as many wall warts as you can find around your house, you'll note that they're all rated for MA not mah. Pop the cover off your cell phone and look at the writing on the battery, you'll likley find a 800-1100mah battery.
A device will be rated for voltage, and for current (generally in MA) never mah's. The MA rating of a device is it's maximum power it can draw not it's continuous one. Typical power supplys don't force amperage, they provide voltage and allow amperage to flow based on the device's effective resistance.
There are some power supplys that are constant current which will provide a fixed current producing as little or as much voltage (up to a maximum) as they are able to, these are sometimes found in older laptops, the bulk majority of all modern power supplies that you find in use will be simple voltage sources with a maximum amperage rating.
The biggest problem with saying all this is a typical wall wart will never actually produce the fixed voltage printer on it's outside, if you measure the output of a transformer based stupid power supply (wallwart) you'll see that the voltag when nothing is drawing power from it can be quiet high, and as the load increases the voltage will drop. The rating on the outside is supposed to mean the voltage that the power supply will be at when the listed amperage is being drawn, but this can be quiet variable with manufacture variances especially with cheap Chinese made power supplies. Most cell phone and more small device power supplies are small switch mode power supplies, the transformers are much smaller and switching is used to produce the output, they're smaller lighter and better they're voltage regulated unlike typical wallwarts.