You should also be aware that Google purposefully tries to make it's bots undetectable and/or blend in with regular user traffic. This is to thwart spammers who would try to serve different landing pages to Google's bot vs. a regular human. In the past they would attempt to serve hundreds of thousands of spammy, over-optimized, auto-generated pages to it's bots in an effort to rank better.
As a result, some third party tracking solutions, and especially home-grown tracking solutions, can often get screwed up by this and report inflated traffic numbers whenever Google's bot spiders their sites. One particular instance where I have seen this happen a lot is when a user sets up a new AdWords campaign. By default, Google will send bot traffic to the designated landing pages, coming from all the keywords in the campaign. So if you added 100 keywords, and 5 ads to a campaign, you may get about 500 bot visits to your site. Google is checking the relevancy of the keywords in your account to the landing page you are sending them to.