If you're looking for epic battles, look no further than Eve Online. Last night more than 4000 players engaged in combat as two of the largest corporations TEST Alliance and CFC battled for control of the 6VDT region. The battle lasted for six hours, and at the end of it more than 3000 ships had been lost.
CCP Games' Software Director Erlendur S. Þorsteinsson tweeted:
"The fleet fight in 6VDT-H tonight is the largest ever in EVE, topping at 4070 pilots (so far). Previous was P-2TTL at 3615. #tweetfleet"
You can find more details on the battle here.