I don't really have much to add to the question in the title.. Is it possible to wake a computer via a wireless network card? (Assuming that a wireless card doesn't consume enough power to make putting it to sleep not worth it)
Yes it is, so long as you have a fairly new wireless card - Intel vPro branded machines do have this feature. You could also use Intel AMT (which can be made available over Wireless) to power up machines.
Technically, WoWLAN support within the operating system needs to be present as well - Windows 7 comes with this kind of support.
There is no technical block to WOL working with wireless, it's all down to whether it is implemented in the hardware and whether the wireless NIC is active when the machine down. For machines with built-in wireless NICs this is quite easily implemented but historically hasn't been for a number of reasons. One such reason is the fact historically only portable devices operated wirelessly and it would generally be considered quite undesirable to have the device woken up remotely. With more and more fixed systems using wireless we can expect to see an ever increasing number of such devices with WOL support.