Co-op account asks for Google API Key information, though it's not required. Also providing this information enables us to check weight more often. Why does co-op ask for Google API Key? How is Google API Key related to co-op???
co-op checks what your pagerank is, and how many pages are indexed from your website, and checks each page for the co-op ad. It queries google using the Google API, and Google API only allows 1000 queries per day. My guess is Shawn has a few hundred/thousand API's or a special setup with Google, and when he runs out of queries, or your account runs out of queries, it asks you for a free google api signup. Pretty simple. Somebody might be able to better explain then me
I think it basically uses the google api to check for the co-op ad? I need a little more clarification as well, I entered it, but had no idea what it actually did.
It allows you to revalidate/recalculate your weight anytime you want. If you don't enter it, you have to wait for the system to recalcalculate your weight every few days. (unless you become de-validated, in which case you can revalidate whenever you want)
Here's an extract from the new, unoffical co-op faq: Google API Key Without a Google API key, the system will validate your pages by doing spot checks every now and then. If you do enter your own API key into the Account Settings then you can validate as often (up to your query limit of 1000) as you like. Useful for instance when you just added a boatload of pages and want instant weight recalculation without having to wait for the bot to drop by. The API key, however, is a source for many of the issues mentioned under Trouble Shooting. Main reason being this query limit. If you use the same key for say the DP Keyword Tracker and other tools it might well be that you are out of queries for that day. Clicking the 'validate now' link will then result in ads not found and a whopping 0 weight, so... Source: http://co-op-faq.blogspot.com/2005/03/5-setup-validation.html