I know that tech is always going to get smaller with time. But, don't most devices and computers come with wifi now? Even if you had a desktop without wifi, having a small adapter like that won't work that well IMO. I guess if someones wifi card went out in their notebook/netbook it could serve as a replacement.
Why is this a downside for Mac users? This device is presumably for laptops, since the physical size doesn't matter much when you're dealing with a desktop. Mac was an early adopter of Wifi in their laptops, with it being built-in as standard while most Windows laptops required a PCMCIA card. Finding an Apple laptop that isn't already equipped is really going back a LOT of years, so it makes sense that this device is only for Windows. Now hopefully it supports the *older* windows operating systems like Windows 2000 and Windows 1998, since those are the likely OS's on such old hardware.
even on modern computers this is usefull. For example Hps dv 6000 have defective M/Bs where the mini pci slot will die winthin 2 years. Whats in that slot you ask? Why your perfectly good mini wifi card thats all. So now you have a good internal wifi with a bad M/B slot with no way to fix it without paying HP aprox 420$ for a repair. So a 12$ micro adapter such as this should work perfect in your home without messing up the lines of the laptop and running the risk of it falling of your lap onton the couch and breaking the longer adapters. Also many many many people still have laptop without wifi. Due to the suposed resession people don't buy new laptops as often as they like so they come into my store every day for possible upgrades to get another year or two out of it. I sell about 3 usb wifi dongles every day mostly to the older genereation but there is still a very strong market for it.