SOPA violates everything Safe Harbor stands for... as a forum owner, it pretty much means that you are responsible for every post your users make.
I don't see how this makes a forum owner responsible for every post they make. If someone posts copyright content upon your site now, then there are already laws to enforce you to remove such copyright content. If you fail to do so, then you get shutdown.
This is also only a US law, and whilst this linked wiki pages states it allows the US to action things in other countries, that is not up to the US to decide, and is up to the specific countries themselves. The US ringing another countries ISP trying to enforce something that hasn't been approved within that country would only fall on deaf ears.
The document clearly states they will only see this ending up in endless legal challenges and will go nowhere fast.
It means that if a company doesn't like a single post on your website, they can FORCE your host to shut you down...
That is being a bit dramatic to be perfectly honest. Again, if a user posts material that is copyright to someone else, then that person has a right of law to protect their copyright. You either remove it or get shutdown.
It basically makes it so you are guilty, until proven innocent. Its a complete violation of everything this country was founded on, and if it passes... America is over.
Well, most other countries already have such laws... and I have had sites "suspended" myself for breach of copyright by going to the US host already, before this law was introduced, because hosts typically already have these terms and conditions within their own policies to replicate existing laws.
If you can send a host sufficient proof to act, that something hosted on their company servers is in breach of existing laws and their policy, they remove the content themselves or suspend the account until the content is removed.
I don't honestly see this affecting every website, but more websites that are doing things wrong by thinking they have some right to copy any content they want and republish it, reuse it, sell it, etc, which is not theirs to rightfully do so with. That stuff is happening and its hard to get action taken...
There are more positives to this than negatives IMHO.