What is the "Maintenance" amount referring to on the bitcoin exchange Bitcoinica?
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.