Why? Because it's blocked by Firefox 3 with the Adblock Plus plugin. I'm not sure if this also impacts FF2. I'm not sure what the percentage of FF3 users are with Adblock Plus, but it gets 317,699 weekly downloads and is Firefox's #2 Most Popular plugin. So it must be considerable. And as we all know...do everything necessary to boost that conversion rate!
FYI, if you're hosting Aweber forms, you may want to change the code a bit.
And Sean...take a break, man! 9,083 means it's time for a beer!
Here's what I do and don't see...