Here is an even better way to hit them in the bottom line...

Add this somewhere in your webpage (you can just stick it somewhere in the footer)

<a href="http://www.namecheap.com">Domain Registration</a>

GoDaddy is #1 in google for "Domain Registration", but if enough people link to this (it doesn't take much) they will be nocked out of the coveted top spot. This will be a huge dent in their revenue stream.

This is referred to as a "google bomb" and it works by the fact that search ranking is based upon the the weight of the links pointed to a page. The name of the link helps them correlate the search terms that match with the link.

Namecheap was chosen as they have a high ranking (so they have a good chance at popping to the top) and has been vocal in being anti-SOPA. You can use the coupon code "SOPASucks" to get a discount there too.

I just added it to two of my sites - editthis.info and cueflash.com (both with a page rank of 5). That will hit them in the SEOs.