"Clickwrap" refers to situations where you have to click through before using the service, hence the name. Agreements which are simply a passive notice in a footer somewhere are called "browse-wrap", and are much less likely to be considered enforceable:
The line is blurred between clickwrap and browsewrap -- those are colloquial terms to describe ToS notices, not legal terms. Is it still browsewrap if you say "By clicking any of the links on this site, you agree to the ToS"? How far away from the clickable buttons must the statement be to be browsewrap instead of clickwrap? The distinction is really only a technicality in the wording, not anything substantive. In practice, you are still being forced to agree to a binding contract (many of which remove one's right to sue in a court of law) just by going past a landing page.
Even if we entertain a distinction between browsewrap and clickwrap, browsewrap is generally enforceable, especially after minor modifications to placement and/or font size.
It's by design because the vast majority of people don't care about that information and it makes the website worse for them to have a big ToS banner at the top of your page.
I don't think many websites have a secret ToS that they hope you won't read, I think most of them don't even know what their own ToS say. I signed my lease on a site with an explicit checkmark for ToS that said I agreed I would only use exactly IE7 to use their site.
Neither of us has explicitly mentioned a jurisdiction, but assuming you, like me, are referring to the United States...
I suppose I can do no better than quote from the Wikipedia page I linked:
> The Second Circuit then noted that an essential ingredient to contract formation is the mutual manifestation of assent. The court found that "a consumer's clicking on a download button does not communicate assent to contractual terms if the offer did not make clear to the consumer that clicking on the download button would signify assent to those terms."
The same page cites a number of cases where a "browsewrap" agreement was found unenforceable and only one where one was found enforceable - and the latter, for what it's worth, involved a sale taking place through the website rather than anything resembling passive browsing. Of course there exist other cases not listed; and there are situations that muddle the distinction between clickwrap and browsewrap. But at least, the very common pattern of, as you said, burying "a notice in the footer of each page" without anything vaguely resembling active consent, as practiced by probably the majority of commercial websites on the internet, seems to pretty clearly fall on the unenforceable side of the line based on those precedents.
Heh, fwiw, there is another one, shrink-wrap agreements, where you can't read the agreement until you've removed the shrink-wrap but doing so means you've agreed.
https://en.m.wikipedia.org/wiki/Browse_wrap