Anonymizer is what we use, they've been subpoenaed and they don't keep any records to subpoena. Aim> Direct connect > nestat -ano 4 > screenshot, that's all it takes.

Actually, the authorities can trace you back even if you have dial-up. Though the case was a murder not a simple online threat. I watched as the FBI subpoenaed mapquest for records of IP addresses requesting map searches of a small town in Iowa before the time of the murders. Some they gave them were AOL accounts, AOL was subpoenaed to handover some history and other info which led them to the guy's mothers house where he did the original map search from another state.