The law is primarily aimed at digital piracy issues (things like people posting entire movies, etc.) but as it currently stands, it is very vague, and likely won't help much with its actual goal. And, as a side effect, would have massive freedom-of-access issues for many legitimate users of these and many other sites.
There's no doubt that this is a complicated issue, so there have been some excellent explanations of what's going on.
Briefly, the DMCA (Digital Millenium Copyright Act) covers sites in the United States, but is focused on a single user. If Johnny posts something on a site that is under copyright, and the copyright owner files a formal complaint, then the site is supposed to take specific actions (and sometimes, everything moves into a legal suit.) It's a pain for the content creator, and not much fun for Johnny - but everyone else can continue using that site without trouble.
SOPA and PIPA, though, are aimed in part at sites outside the United States (where a lot of pirated work is hosted) but are written so vaguely they can also apply to sites within the US, or sites (like YouTube, Wikipedia, and all sorts of other places) where there's a bunch of awesome user-created material, but also some material that is posted without the copyright holder's permission. In these cases, if the law passes, the US government could choose to shut the entire site down - no access for anyone in the US.
See why people are calling it vague? The best analogy I've been able to come up with is that it's like teachers who say "Just because one of you has been bad, none of you get to go to recess." Ever. And then they enforce it by putting padlocks on the playground, so no one else can get in either, even before or after school.
That didn't work terribly well when we were kids - and it certainly doesn't work very well when you're talking about thousands or millions of people. (And especially when many people are deeply confused about copyright, as lots of people are, and a lot of things like exactly what a derivative work are up in the air still, in terms of legal precedent.)
The basic intention's reasonable enough. But don't we deserve a better designed law?
What can you do?
- Inform yourself - there are great posts from a couple of fellow librarians (Jessamyn West, Brian Herzog) and technology geeks (BoingBoing) as well as a bare bones infographic.
- Once you've decided what you think, get in touch with your legislators (there's more info at both the first two links) and tell them.
- Tell other people why they should care - pass this post on to your friends, neighbors, whoever else you know who uses the 'Net.