The trick is figuring out how many users would use the Firefox search box vs would just enter google.com into the URL the old fashioned way (or would change the search box back to Google). I have no doubt Google is measuring that number and used it to guide their bidding.
My hunch is that Google is only breaking close to even with this deal (i.e. making $300M for paying $300M) and bid high just to keep too many people from trying Bing.
Plus, Google tends to act at least a little altruistic when it comes to the web [1] and may mind less being generous to Firefox.
Hunches aren't very useful without hard data. More practically, defensible logic is good practice on HN, because people try and build real businesses based on what they read here.
A month ago many people thought that Mozilla was going to be in financial trouble because "they couldn't re-sign the Google deal". That seemed to be based on little more than a hunch, which data showed that was clearly wrong (which I pointed out at the time).
Note that a donation to Wikipedia is very different (for tax purposes) to a business arrangement with Mozilla.
(I do agree that Google is good to the web though)
My hunch is that Google is only breaking close to even with this deal (i.e. making $300M for paying $300M) and bid high just to keep too many people from trying Bing.
Plus, Google tends to act at least a little altruistic when it comes to the web [1] and may mind less being generous to Firefox.
[1] http://wikimediafoundation.org/wiki/Press_releases/Wikimedia...