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.