What is the "Maintenance" amount referring to on the bitcoin exchange Bitcoinica? I have tried out Bitcoinica, and although it is complicated i like it a lot!

What confused me is the "Maintenance" amount shown in the Account overview. It looks like it is not explained on the website.

If it is the fee, it is quite steep, i must say..
No, it relates to when you have a margin call for your open positions. From their FAQ:


  What's your Margin Call Policy?
  
  After you've logged in, you can immediately see your real-time account
  Net Value (total assets) and Maintenance (minimum net value). When
  your Net Value falls below twice the amount of Maintenance, we will
  issue a margin call. If you don't take actions before your Net Value
  falls below Maintenance, all your positions will be liquidated
  automatically.