The traditional afk-exp method is to grab a Warrior, shove him in some -DT gear (and preferably a RDM to give him Phalanx), gather up a metric fuckton of mobs, and have him use the Great Axe WS "Fell Cleave" on them, then Retaliate back to full TP almost instantly and repeat.
SE apparently started cracking down on the RMT cleave parties, though I suspect that quite a few cases of people being "banned" for it are simply people using an excuse to hide the fact that they hacked their asses off in Neo-Nyzul.
As for the rest... I've cleaved for people, lol. Though not especially efficiently; really need WAR to do that. I've contemplated leveling WAR for that very purpose though lol, since I have a decent set for it.
What Foo did, however, was simply fall asleep in a regular burn alliance at the worms in Abyssea La Theine lol. I was there at the time (I was his party lead, in fact), and I knew he was sleeping when I logged off lol, but it's Foo, I make allowances. XD
Experience in Abyssea works a bit differently than normal. Mobs start out at a specific amount relative to your level, but every kill of the same mob raises that exp. You can actually start killing mobs and get no exp at all for quite a while, but it will climb fairly quickly. Certain chests have lights that allow that exp to go higher. In the aforementioned party where Foo passed out, for example, I was getting around 600 exp per kill, and had gone from 77 to 95 in that party.