this is only a problem if you have a wife
People are finding new and exciting ways in which GFWL sucks all the time.
You can only have a profile on once and your GFWL is most likely signed into your same Live ID as the XBOX's profile uses.
In my opinion, Microsoft screwed the pooch on how 360 profiles work. It's a huge pain to be able to use the same profile on multiple 360s... you actually need to put it on a USB thumb drive and physically switch it.
Yeah, I actually bought a 256 MB memory card just to keep my gamertag on it so I can log in from a friend's house without having to recover my gamertag.
I have one as well, but they're now absolutely useless. The problem is that they do not work on the newer XBOX 360S and you're required to use a thumb drive instead. It's not really a bad thing since those memory cards were terribly overpriced anyway. I bought an official used one from GameStop and I think it cost me around $15-20 :\.
You also run into problems with games that refuse to let you transfer their save data. It's a huge joke how restrictive these consoles are, but most people don't run into it, because they only own one device. It's the same issue with trying to play games on iOS devices. It's fine if you own one, but if you own two (iPhone and iPad for example), it's utterly impossible to sync things (for 99% of the games) without hacking both devices.
I hear you on the iOS device thing. My wife and I have iPods and I've always wondered why you can have profiles in the iTunes software. My solution was to install iTunes on the HTPC and just keep my stuff far away from her stuff. I don't support DRM laden music anyway, so it's not a huge deal for me. Got an iPod due to car audio gear pretty much only supporting iPods for direct digital connections to your gear.
It's the same issue with trying to play games on iOS devices. It's fine if you own one, but if you own two (iPhone and iPad for example), it's utterly impossible to sync things (for 99% of the games) without hacking both devices.