I have many websites on a server and none of them has seen [google.com...] in 30 days. I am well indexed in Google and doing well. I did start using a Robot.txt about a month ago. I am not blocking GoogleBot.
Big changes in googlebot recently, and also in all Google crawling. You may now be getting visited by other bots that Google operates, such as the AdSense "mediabot" and that crawl is being held in one universal Google cache.
This is what googlebot will put in your site log file "Googlebot/2.1 (+http://www.google.com/bot.html)"
This is what the adsense spider will leave in your site log file "Mediapartners-Google/2.1"
In fact, Google's feed spidering and news spidering are now also sharing the same cache with the regular googlebot. See [mattcutts.com...] for more information.