Not so...there are considerable differences between one and another wall-wart (charging wall blocks). Some are very good at smoothing out the power to eliminate or minimize any fluctuations in voltage, reduce or eliminate any Radio Frequency Interference, and make sure that the current is consistent (Motorola chargers are one of them). Others are much less successful at minimizing these effects. The result for me has been that when using a non-Motorola charger on either the Droid 1 or Droid 2, and if I was trying to use the screen (digitizer) to scroll or select, the dirty power of the non-Motorola chargers caused the screen to be jittery and in some cases downright unresponsive, instead jumping all over the place, selecting things, moving icons, starting apps, etc., all with only one finger trying to scroll the screen. Disconnect the rogue charger, plug in the Moto charger, and the problems disappear.
I believe that for charging only, as long as the charger is rated at 800-850mah, it will do a fine job of charging, but you are likely to have the difficulties described above if trying to use the phone while plugged into one of these non-Moto chargers. It also didn't seem to matter if it was a name-brand charger or a China import no-name.