That will drastically cut down on the boilerplate. Want to straitjacket your users with 60 pages of user agreement? No problem! You're only 60 button clicks away from complete lack of liability.
That said, one can scroll rather quickly.
I think if the technical details with screen-size and tracking what was indeed visible at the time of acceptance are worked out, that this is a great idea and really would use market forces to naturally shorten TOSs. It has a very Libertarian Paternalism idea about it in that it's not limiting freedom but gives them a Nudge[1] in the more universally beneficial direction.
As a user who just wants to click accept and GTFO, this would initially be a burdon as all existing TOSs are aligned with this requirement. I don't want to accept 60 pages just to install WinRar (the trial of course, because I'm still not sold on it's benefits).
But as someone concerned with what I'm actually agreeing to, and someone who doesn't have the time to read the TOS for everything I come across, I'm fully behind that and would like to have some words with the lazier side of me about the importance of agreements.
As an aside, maybe there could be an article of the law that allows for a legally binding summary of terms which they could use to supplement the full terms. In that case, the user would be bound to the terms of the summary--in reference to the full terms--which were visible on the screen when they accepted. They would still be required to accept the full terms (likely with the same TL;RD scroll and accept).
I'm thinking that there's somewhat of a precedent to such summaries: ballots. When you vote on on a resolution at the ballot, you're reading a summary. But that summary has to be legally accurate to the content of the bill.
[1]http://www.amazon.com/Nudge-Improving-Decisions-Health-Happi...
edit: really, this is the exact same problem as "some people have taller screens than others", but some people have taller browser windows than others too. If I want to get some text off screen before clicking "I agree", it's fully within my power to do so.
The point is that when we allow arbitrarily complex language to be buried under a single agreement action, a user has no idea what they are actually agreeing to. And everybody knows it. So we should just make such agreements null and void until the technology community (us) and the lawyers can come up with a way of breaking these user agreements down into digestible, understandable units.
While I would not agree that users should be held liable by terms as either criminal or civil infractions of any sort, they certainly work well to advise the user of what services they will be provided, under what circumstances the provider will be justified in removing service, whether or not the customer will be refunded in those situations, etc.
As a declaration of intent of service, potentially usable defensively by the company should a user take umbrage against the service, they are excellent. As anything else, they're pretty worthless.
Which unfortunately destroys the Internet until that happens. Businesses typically don't enjoy the benefit of the doubt and consumer protection laws that their customers usually do when those customers sign up with a standard form contract where they have little if any power to negotiate. If a business offering a product or service isn't able to define reasonable terms to clarify what the deal is then that business can't transact with customers without accepting an absurd amount of risk or without negotiating individually with each customer at prohibitive cost.
When we did the terms for a UK business not so long ago, we were advised that things like hiding potentially unexpected terms away could weaken those terms if we ever tried to enforce them, while if certain terms that are reasonable but not necessarily obvious are emphasized then this can strengthen their enforceability. Also, there are some basic legal standards that any such contract would have to meet, e.g., where consumer protection laws say that certain kinds of term are completely prohibited.
This seems a reasonable fundamental policy: whoever is writing the terms can't rely on unreasonable conditions, and if there's something reasonable but possibly unexpected then it's in their interests to draw attention to it explicitly, but assuming they do those things their terms should be expected to stand up in court if necessary.
There is - both in theory and in practice. Otherwise you'd get text drawn over other elements instead of scrollbars when you write too much text inside the edit box.
Sorry if that's not what you were asking, and note there are lots of different ways to do this, that's just one example.
I could see the EU implementing it as part of its ongoing privacy/transparency efforts, but I doubt the US Congress would be of any help.