Friendlist groups - purpose?

Having to deal with the daily RMT tell spam, and knowing we can "classify" our friendlist in groups, I've come to wonder what the real purpose of this is.

You can get sound notifications for different chat modes, yet you can't assign a sound to a specific friend group. Is the whole purpose of assigning a group so you see a fancy icon before their names? And only on the chat log? Normally a group has a further purpose, example on phones, you assign a sound to the entire group, or make it silent, send a message to the whole group or which ever.

I have tells in a seperate tab, I still am mostly on /busy but when I'm not, I would find it awesome if I get a tell from a specific friend group and get a sound, so I know it's not a spam and bother activating that tab.

Can we have a real purpose to friend groups please?

I think the original purpose was simply so you could identify who was who - how you knew people or why you friended them in the first place, and for better sorting of the Friend list for people who have extensive ones. (Incidentally, I think the blacklist should have groups too, so we can distinguish RMT spammers we've blacklisted from legitimate but obnoxious players we blacklisted.)

I like your ideas for adding more functionality to the groups, though.