Former Facebooker Scoops Up $1.4 Million for Freshplum (YC S11) 14 years ago
I was thinking that there should be a plugin LevelII stack for each good, say used computer hardware. you can hit someone's bid or put your offer away from last traded price.
http://www.yourtradingjournal.com/images/nt/NinjaTrader_clip...
I'm sure that for virtual goods, delivery is more fluid and there would be less of difference say for an identical configuration of a server, but one server with 8GB vs 16GB ram.