Just checked my messages and realised I had an invite in my inbox from two weeks ago.. hah.
One thing I just thought of that I think would be a great addition is Friend nicknaming/tagging.
After adding a few people from GAF I realised that whilst I know where they added me from, I might forget. And there are always those few friends on your list from a year or so back that pop up or you invite them and forget how you know them. This is the internet after all, you make new friends, sometimes you drift apart, such is the world. It'd be great if you could remind yourself who is who (especially when Gamertag's are often so obscure) with a custom tag. Similar to how Steam lets you nickname people completely, only maybe not so extreme.
So you could tag anyone from GAF with 'NeoGAF' or someone from Reddit or wherever, and it'd show up next to their GT. Or if you got chatting with someone whilst shootin' it up on CoD and added them, you could tag them as CoD Ghosts, and in a year you'll remember that you became buddies through CoD. Of course your real life and close friends you don't necessarily need to tag because you aren't likely to forget them but even so you could use it and tag them with their nicknames if you so choose.
Just my suggestion. I don't know if there is an actual place to submit ideas to Microsoft but please enlighten me if you know. I wondered whether or not to make a thread about the idea but it isn't really worth it so here seemed the most logical place to post it.