NOTE that the Registered Trademark of "1-Click" will still be valid and owned by Amazon
http://tmsearch.uspto.gov/bin/showfield?f=doc&state=4808:d4r...
http://tmsearch.uspto.gov/bin/showfield?f=doc&state=4808:d4r...
You could enforce it with additional restrictions, like color / size / font / layout, but the text "1-click" can freely be used to describe processes that require 1 click.