With so many saying that google's stock is way overvalued, building a national wireless network or just a 'regular' ISP may be the best way to throw around the weight they have now to establish a truly permanent foothold.
Also, (this is a stretch, but) it's been argued that the youtube acquisition was in large part due to google's want to put their warchest behind keeping the DMCA's definition of 'common carrier status' as wide as possible. This is something they definitely need to protect as a search engine, but also certainly if they want to become any form of ISP, especially one with open wireless networks.
If every single person in the country had broadband access, regardless of economic status, there's no one that would benefit more than Google. The pay-access model of the current ISPs is in their way to greater market penetration. Add to that the (quite accurate) location data that wireless would give them.. the possibilities are endless.
Also, (this is a stretch, but) it's been argued that the youtube acquisition was in large part due to google's want to put their warchest behind keeping the DMCA's definition of 'common carrier status' as wide as possible. This is something they definitely need to protect as a search engine, but also certainly if they want to become any form of ISP, especially one with open wireless networks.