Today, Wikipedia is not available to us — at least not easily (you can still view it on mobile devices and also in your browser with some tweaks). The reason is that it is part of a protest against SOPA and PIPA — two pieces of legislation being considered by the US Congress. To read the commentary on this, to an outsider like myself, the whole exercise seems broadly insane. Anyhow, the best articulation of the problems is this letter signed by 110 legal scholars. Here is a good video treatment. From that description the proposed legislation is far reaching while at the same time likely to be ineffective in its true intent (to stop copyright infringement). It also appears to be woefully inconsistent with the way Internet technology is evolving. But the notion that enforcement and prevention matters will be put in place that create massive harm to the lives of innocent individuals while being unlikely to really actually led to less of the activity targeted is not unprecedented. You can think about this every time you go through a US airport and think about who is winning there.
In thinking about the US airport case, it is useful to forecast what the outcome would be. First, will someone take down Wikipedia even if it is likely to be breaking this law? Wikipedia break this law by linking to ungated copies of academic papers. To be sure, it is some Wikipedian who has generated the link but the law requires Wikipedia to deal with it. On the one hand, this seems unimaginable. At least initially, one suspects that very naked copyright infringers will be targeted and I am assuming that copyright holders already have their targets in mind. On the other hand, while copyright holders in movies or music may not care about Wikipedia, those in academic publishing will. For them, they may regard Wikipedia as the naked infringer and it only takes one of them to seemingly initiate a process of take-down. In that situation, will Wikipedia actually remove the identified links? That is a trickier question. What is most likely is that Wikipedia will be asked to change the links to gated copies of the papers. Eventually, however, someone will hold-out on even those requests and the true fight will ensue.
Of course, the issue here is that, based on current processes, which involve fairly manual search for infringement, by making it easy for sites to be taken down, the incentives for copyright holders to automate the process of identification and notification will be high. This can matter. A few years ago, an Australian news organisation sent me a take down notice for blog posts that quoted from their content. To be sure, the content quoted was opinion pieces I had written for them and received no payment for nor had signed any copyright agreement about. Moreover, and I am not making this up, the letter demanded that I publicly state the infringement and announce the request to remove it. The letter was very threatening and cost me an afternoon finally reaching the general counsel of the company in question. The general counsel correctly realised that if I actually complied with the letter it would create very bad publicity (they literally asked for it) and blamed it all on an overenthusiastic summer intern. The point is that had this been automated with the media company going to a hosting service or ISP and that firm simply removing my site, there would be no ability to negotiate or sort it out. I would have faced more than an afternoon of calls to get this back and instead faced prohibitive legal costs.
So the scenario that US people should be concerned about is if publishing on the Internet becomes like airport security. That is, if copyright enforcers are able to automate enforcement without due process. That will raise the costs of publishing and will deter many. As is often the case with over-reaching laws, the problem is that it creates too few incentives for enforcers to enforce discriminately rather than indiscriminately.