The places where the iPad did charge, in their tests, included an iMac and a MacBook Pro. The iPad would not charge using any USB ports on several Windows machines, nor through the USB port on an Apple wired keyboard connected to the iMac.
They're not the only ones to notice it. Our own Steve Sande just noticed that his iPad, which is linked to a USB hub connected to his iMac, is not charging through the hub. Apple's tech note for iPad charging covers some of these contingencies.
Apple Tech Support told Consumer Reports that the iPad was designed to be powered using the wall charger. Dave Caolo also was informed by Apple retail staff that using the iPad charger to charge your iPhone is not recommended.
If you don't have a Mac, for now you're better off using the wall charger to power the device. Have you found other places where the iPad is not charging? Talk about it in the comments, or click through and let Consumer Reports know as well.