Do you really think it could be that easy?
Hell, if that was the solution, I'd no doubt be using the 'BristolBachelorBot' search engine, today, wouldn't I? The reason why there's only one serious contender, and one wannabe, in this market, is because it's hard.
Even if those factors didn't alert you that a search engine was on-the-visit, the very fact that it reads your Robots.txt file is a bit of a giveaway. I'm sure you wouldn't advocate search engines stop reading robots.txt?
Google regularly and deliberately haze the behaviour of their search engines, to throw these people off, but its a constantly moving battle. I really don't think people outside of search, realise the enormity of the problem of automatically gathering realistic data on the Web, these days. We only notice it, when it fails.