Power will always be abused. It’s a rule. Look it up. Also, read this:
The Federal Bureau of Investigation used false terrorism emergencies to illegally collect more than 2,000 phone records between 2002 and 2006. A series of e-mails and memos obtained by The Washington Post details how FBI officials violated their own procedures and strained their communication analysis unit with non-urgent requests. In many instances, approval was granted after records had been collected to justify the FBI’s actions.
See? Also, the software and databases that your favorite online services use to make it easier for law enforcement to gather surveillance on you are big, juicy targets for malicious hackers.