Let's break down this warning:

• "For Official Use Only" — This means the information is sensitive, but unclassified. If this is true, then USASpending.gov contains information that should not be released to the public. It is unbelievable that the government would put information that is actually For Official Use Only on the Internet!
  
• No expectation of privacy — This is in direct conflict with the website's privacy policy, which opens: "the privacy of USASpending.gov customers is of utmost importance." It also says that no personally-identifying information is automatically collected when you visit USASpending.gov. The warning and the privacy policy cannot both be correct.
  
• Unauthorized activities — What exactly would be unauthorized? If the information on the site really is "For official use only", then it is unauthorized for a private citizen to even access the information.
  

This is the scariest warning I have ever seen on public government information.

Luckily you don't need to use USASpending.gov; there are alternatives:

• FedSpending.org has the same information, interface, and API. USASpending.gov was meant to duplicate FedSpending.org anyway. But let's hope that the Sunlight Foundation continues to support FedSpending.org.
  
• Paper editions of the federal budget are still printed and kept in your local Federal Depository Library.
  
• A great map of federal contracts by state was created from the FedSpending.org database. Future government mashups may become available at ProgrammableWeb's Government API page.
  
• If you feel brave, you can try exploring the budget online at the OMB webpage.
  

Although there are other ways to get federal budget information, the warning on USASpending.gov is unfortunate, because it is wrong and it violates federal policy. USASpending.gov does not meet the definition of "For Official Use Only"; it contains public information. There is an expectation of privacy; no personally-identifying information is collected from visitors. The warning conflicts with OMB Memoranda, which require each government site to "post clear privacy policies" and adhere to them, because the warning significantly obscures and confuses the site's privacy policy.

USASpending.gov might be a good resource, but the intimidating and incorrect warning on the home page needs to be removed before it can be a tool for government transparency. In the meantime, use FedSpending.org.