I posted this last june.
Ok, let me all tell you a little story.
The year is 1998. A 16-year old college freshman has his first high speed (10Mbit) connection to the internet at one of America's 10 most internet friendly schools (at the time anyway). The student also has a fresh new Debian install, and a copy of wu-ftpd.
The student begins to rip all of his CDs into MP3 format. It's convienent. The student also gets CDs from others, MP3s from others, and finally MP3s from various little FTPs at other colleges.
By early 1999 the MP3 collection is at a quite large 12GB. It's quite large for the time anyway. So what does the student do? Puts up an FTP server. Just 10 users. The music is free, he just asks that you upload something cool for his troubles. Many do. The student gets pre-release albums and some weird things he's never heard of before. Sometimes copies of programs or even the occasional porno movie out of nowhere.
The student's computer is pretty good, but has lots of hot components in it. It's fairly cramped up, and the hard drives are the oh-so-unreliable Maxtor brand.
The student leaves for a while and what happens? The computer heats up on an especially hot day. The hard drive fails, or atleast part of it. The MP3s are still intact, but the FTP configuration file is corrupt. Gone is the limitation of 10 users. In this period the new Lycos MP3 search picks up on the server. It's fast, has lots of content, and has no ratios.
So when the student comes back and the internet access is cut off, he is confused. He checks the logs. Eventually he finds out that 600-1200 people were connected/trying to connect to his FTP server.
Enter the dean. Apparently the student not only took down his dorm access, and not only campus, or city, or county, or regional access, but from the *entire* northern half of the state. Schools, businesses, residents, none of them could access the internet reliably for days.
Enter the FBI. So the student is threatened with confiscation of equipment, etc. Fourtunately this is before the RIAA was *too* angry about this stuff. The student appears before the network admin, dean, FBI, etc and appologizes. Luck comes into play and the whole thing is dropped. The student is only ordered not to run anymore servers of any kind. He got lucky.
So yes, running an MP3 FTP server can be dangerous. Trust me, I know from first hand experience!