Under the Digital Millennium Copyright Act, rightsholders have an easy way to take down online material they dislike: send a takedown notice to a website or an ISP. The target of the letter has the right to object by filing a counter-notice, but even if that happens, the targeted material must remain offline for 10 to 14 days before being reposted. If this restriction isn't followed, the ISP or website in question could lose its "safe harbor" from lawsuits.
This provision of the law means that the DMCA can be used to silence speech, even in cases where the material has not be found by a judge to be infringing. This was an issue with John McCain's presidential campaign, where news organizations filed takedowns with YouTube about several McCain clips which used their footage. Despite the urgency of the issue (the election was only weeks away), YouTube publicly refused to put the clips back up before the counter-notice window expired; it had the legal right to do so, but the company refused to expose itself to the liability.
DCMA is typical of a poorly drawn up law that hasn't been thought through. The UKs proposed Digital Economy Bill is following in it's footsteps. Some of the implications of the UK bill are horrendous. It will be interesting to see how effective opponents will be at showing just how badly this bill has been drawn up. Hopefully, after the UKs current election, some of the huge mistakes will be rectified by the new government. We can hope.