User blog comment:DaNASCAT/Technical Update: July 5, 2011/@comment-3235402-20110711113332/@comment-26686429-20110711113636

Depends on what you're doing. Take the following URL:

http://community.wikia.com/wiki/User_blog:DaNASCAT/Technical_Update:_July_5,_2011
 * If you add ?action=purge to that, it'll work - so

http://community.wikia.com/wiki/User_blog:DaNASCAT/Technical_Update:_July_5,_2011?action=purge purges the page, but - if the url already had a ? in it, let's say it was: http://community.wikia.com/index.php?title=User_blog:DaNASCAT/Technical_Update:_July_5,_2011 - then it would need &, to distuingish between the 2 arguments you've given the URL.
 * In general, the first argument to a URL gets a ?, any additional arguments to the url get an &