It's a pretty lame thing, but what's going to happen is what happens every time a legislative body comes up against nerds - the nerds find a way around it.
Alternative DNS root servers are already in place, and if SOPA goes through, we'll just use those.
Will it undermine the integrity of the DNS system? Yeah. And that'll suck. But that'll be the extent of the damage.
What they will actually end up doing with these laws if they pass may be one thing. But what they would be capable of doing is a lot more than I think you realise. Example, you post a copyright infringing video on youtube. The government can shut down youtube. This law basically allows them to take down a site for having copyright infringing material on it, regardless of blame.
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