eWhisper - 2:08 pm on Jan 18, 2005 (gmt 0)

I'm not a cookie expert, but this is how a G employee described the above to me.

When someone clicks on your ad, a cookie is placed that associates that user with that account. So, while your landing page doesn't have a customer ID in it, it doesn't matter because the cookie has that info.

The other reason that was stated as to why the code doesn't have one is that it makes it so competitors/others can't pull any account info from your site code or use your conversion data script on another page (that you don't own) to mess up your stats.