EFF has posted their study of the unintended consequences of the DMCA.
Here's a quick run-down of the consequences:
Chilling Free Expression and Scientific Research
DMCA Delays Disclosure of Sony-BMG “Rootkit” Vulnerability
Cyber-Security Czar Notes Chill on Research
Professor Felten's Research Team Threatened
SunnComm Threatens Grad Student
Hewlett Packard Threatens SNOsoft
Blackboard Threatens Security Researchers
Xbox Hack Book Dropped by Publisher
Censorware Research Obstructed
Dmitry Sklyarov Arrested
Scientists and Programmers Withhold Research
Foreign Scientists Avoid U.S.
IEEE Wrestles with DMCA
2600 Magazine Censored
CNET Reporter Feels Chill
Microsoft Threatens Slashdot
GameSpy Menaces Security Researcher with DMCA
AVSforum.com Censors TiVo Discussion
Mac Forum Censors iTunes Music Store Discussion
Fair Use Under Siege
Copy-protected CDs
Fair Use Tools Banned: DVD Back-up Software
Advanced e-Book Processor and e-Books
Time-shifting and Streaming Media
embed and Fonts
A threat to innovation and competition
DMCA Used to Lock Cell Phones to Carriers
Apple Threatens Real over Harmony
Tecmo Sues to Block Game Enhancements
Nikon's Encrypted RAW Format Blocks Adobe
HP's Region-Coded, Expiring Printer Cartridges
StorageTek Attempts to Block Independent Service Vendors
Lexmark Sues Over Toner Cartridges
Sony Sues Connectix and Bleem
Sony Threatens Aibo Hobbyist
Sony Attacks PlayStation “Mod Chips”
Blizzard Sues bnetd.org
Apple Harasses Inventive Retailer
DMCA Shoulders Aside Computer Intrusion Statutes
Disgruntled Company Sues Former Contractor For Unauthorized Network Access