The following attempts to document and explain the anti-abuse system in
TightURL.  Ideally abuse is kept out of the database to begin with, but in
many cases it must be dealt with afterward.
 
 1. Rejection of bad bots thanks to Bad Behavior.

 2. Rejection of invalid URLs.  Since garbage in the database is abusive
    to the operator of the TightURL service, we attempt to keep junk out.

 3. Rejection of blacklisted file extensions.  Much abuse involves getting
    someone to run a Windows executable.  A set of abused extensions is
    provided, and can be updated by the site administrator.

 4. Rejection of locally blacklisted sites.

 5. Rejection of URI blacklisted sites.

 6. Rejection of links to known redirector sites.

 7. Re-checking accepted URLs for those who run the "killbot".