I went to my friend's place today to watch the match between France vs Italy [3-1!!] (and Kuwait won vs Australia [2-0!]) but that's not the story. My friend's younger brother has two Macs, iMac G5 and MacBook 2.0GHz (white), he uses Alcatel Speed Touch modem for his ADSL connection and it connects via USB 2.0 link. His MacBook was connected to his ADSL modem and he wanted to connect it on the iMac to play online games (C&C: Zero Hour) so he had to disconnect the modem, as soon as he pulled of the USB link, his MacBook crashed! When I asked what's wrong he said he doesn't know and this happens everytime he disconnects the USB link. He said this happens to his iMac as well!
I went home, grabbed my PowerBook G4 and came back to try his modem on my Mac and guess what, it also crashed as soon as I unplugged the USB link! It is impossible, in my opinion, to find the problem in our Macs, so I'm quite sure the problem is something with the modem itself.
As for its connectivity speeds, with 1mbps connection it is amazingly fast. It comes with a CD to install drivers on Windows and Mac plus some other applications (that don't work on Mac even though they're made for OS X 10.3+).
Now that I know about this awful downside, I do not recommend it for any Mac users. Besides, I'd rather connect through either Wireless or Ethernet. Why waste USB hub on something like this?