When selling similar domains (let's say 25 domains about the various types widgets e.g. strongwidgets.com, smallwidgets.com, americanwidgets.com...), obviously a one-page site outlining the scope and potential of the site can do WAY more than just parking that domain and collect three cents a week, let alone the limited exposure to potential buyers.
How big is the real risk of dupe content penalties for those sites and what is your experience with one-pagers anyway?