What a bunch of alarmists. The government is not "installing malware & tracking cookies", and they do not have access to your system after you close out your browser session. This is just a government message basically saying if you use the site/system to commit fraud, hack it, etc, you will be prosecuted (if they could even catch you). Additionally, I assume they also keep some of the info you input for statistical purposes (i.e. what models/years are being turned in, etc).
Maybe I'm way too laid back, but that disclaimer doesn't make me feel like the black helicopters are coming to my house. A website I access everyday for work has a similar disclaimer:
You are accessing a U.S Government(USG) Information System(IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions:
•The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct(PM), law enforcement(LE), and counterintelligence(CI) investigations.
•At any time, the USG may inspect and seize data stored on this IS.
•Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.
•This IS includes security measures(e.g., authorization and access controls) to protect USG interests--not for your personal benefit or privacy.
•Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, pyschotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details.
Go ahead and take off the tinfoil hats now...