I looked, but I can't figure out the right Google juice - example.com is, for obvious reasons, a pretty common search result on the web! USENET would be better, but Google Groups seems to not index words with periods in the middle; "example.com" returns only "example com" results.
It was common advice back in the day to use "example.invalid" and NOT kill some poor guy's server at example.com; I don't think .invalid was explicitly reserved before then, but it was known not to be a ccTLD or gTLD.
ETA: I am now starting to doubt my memory here, and Google's USENET archive search is broken. Sigh.