Every search engine that is worthwile (and which you'd want to list you) follows the robots.txt guideline. Also many large sites use them...as evidenced by: http://microsoft.com/robots.txthttp://www.sun.com/robots.txthttp://www.apache.org/robots.txt
Just don't make Sun's mistake and put some files which you may not want the public to know about in your robots.txt file. I'm not sure what's in those Sun binaries in the second row if their robots.txt but it looks like some important stuff.
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