Here's how I see a global chat going down:
[Global OOC] ihavecancer1234588: FAST CREDIT DELIVERY!!!!! 500M/$6.95!!!!!!
WWW.CREDSPAM.RU/LOSER/!!!!!!
[Global OOC] ihavecancer1472898: FAST CREDIT DELIVERY!!!!! 500M/$6.95!!!!!!
WWW.CREDSPAM.RU/LOSER/!!!!!!
[Global OOC] Clantoon142: WTS OVERLYPRICED ITEM! PST!
[Global OOC] Omnitoon455: WTS OTHER OVERLYPRICED ITEM! PST!
[Global OOC] You: hey guys wats up
[Global OOC] Complainer999: OMG THIS GAME IS DUMB FUNCOM SUXORZ
[Global OOC] ihavecancer1478293: FAST CREDIT DELIVERY!!!!! 500M/$6.95!!!!!!
WWW.CREDSPAM.RU/LOSER/!!!!!!
[Global OOC] Complainer593: I KNOW FUNCOM IS LITERALLY HITLER
[Global OOC] Randomdudezorz: YOU ALL SUCK
Sure you could block it off, but I just see global as getting abused way too much. They had global chat in WoW at one point, and it got promptly removed after they realized it was a GMs worst nightmare.