Some activities in this game scale well to 2-3 accounts, some activities scale to 5-10, and some scale to 20-40+. I'd research the general activities in EVE and try them solo with another group of people before multiboxing them.

Some activities that come to mind:
Incursions
Mining
L4 and L5 missions
Wormhole PvE
Small gang or fleet PvP
Ganking
Bombing

I'm sure there are a ton of others that people can add.