Claim to fame:
Operated the world's most popular anonymous remailer, called penet.fi, until he closed up shop in September 1996. Helsingius' troubles started when he was raided in 1995 by the Finnish police after the Church of Scientology complained that a penet.fi customer was posting the "church's" secrets on the Net. Helsingius mothballed the remailer after a Finnish court ruled he must reveal the customer's real e-mail address.

Unusual tools:
Ran the world's busiest remailer on a run-of-the mill 486 with a 200-megabyte harddrive.

Little-known fact:
Never felt the need himself to post anonymously.