Another reason to avoid junk ETFs, from Ameritrade:

Dear Valued Client,

We want to let you know that effective December 1, 2009, the Financial Industry Regulatory Authority (FINRA) is implementing increased customer margin requirements for leveraged Exchange Traded Funds (ETFs). FINRA believes these higher margin levels are necessary in view of the increased volatility of leveraged ETFs compared with their non-leveraged counterparts.

In response to these mandatory regulatory revisions, TD AMERITRADE has decided to make the following changes to our margin requirements:

• Effective December 1, TD AMERITRADE is increasing the maintenance margin requirements for leveraged ETFs and associated uncovered options by a factor proportionate to their leverage (for example, 2X or 3X).
• We will change our margin requirements to 60% for double-leveraged ETFs and 90% for triple-leveraged ETFs.
• Uncovered short options will have a margin requirement increase to 60% or 90%, based on the leverage factor of the underlying security. The base requirement for naked options will be modified to correspond with the equity margin requirement.
• You will be limited to regular buying power (not day trading buying power) for any opening trades in leveraged ETFs.