You can bet the farm that because of this all major online retailers have already started work to change their registration and ordering systems to implement a clickthrough rather than ticking a checkbox that says 'I agree'.
From reading the article linked to in tfa, a checkbox would work. Zappos's problem is that they just buried a link to the tos at the bottom left-hand corner of the page where no sane user would click.
We are not a loved organization, but we are a respected one. -- John Fisher