I've watched quite a few live streams of D3 players, and came up with (i.e. stole someone elses idea) a pretty good strat for pure gear farming for the common multiboxer.

It looks like the current "best way" to farm is to find replentished chests in Act 3 Inferno - which seem to have a good chance at dropping yellows.

So you create a game, only have your main guy in the game. Find a replentished chest, then invite all your alts. Teleport to your main, equip your magic find gear on all your guys. (I have 200+ MF on all guys from just the drops I found). I have all my MF gear in the same order on all my guys (bottom row in my inventory), so it takes about 5 seconds to switch with mouse broadcasting. Shift+alt equips your second ring.

Open the chest, loot all the good stuff, hit "T" to portal back to the town. Leave game on main, find another chest on the main. Repeat.

Act 3, quest 5 has a good shot at a r chest right as you enter the area with monsters - due east and south a tiny bit - about a screen or two over, there is sometimes a stairs leading up to a platform that has a replenished.

Farming locations will probably move or get nerfed, that's just how D3 is, but it's pretty easy to find stuff on one guy, and then invite others to the game to save any hassle.

I did this for a few hours, got a lot of yellows. I got a bit bored and started using all my guys to kill packs and try different specs.