Well, music fans for one.
What is the long tail? In music, its comprised of all those artists and albums that never got much radio airplay, and therefore had little sales. For more background on "The Long Tail" check out this article at the Wikipedia.
So why am I so sure about music fans and the long tail? A few reasons...
#1 Over the last few years iTunes, with their 1mm song catalog (think head, not tail) have sold 300mm songs. Over the same period, the P2P networks, which feature much greater selection (see #2 below), have seen 80 Billion downloads, or 250 times as many transactions.
#2 If you look at the digital music collections of P2P users in aggregate, there are close to 4mm different unique songs being shared. That's 4x the variety of iTunes and other on-line stores and services.
#3 If you look at the distribution of what people have searched for at upto11.net, you will find over 6,000 different songs, albums and artists - and that's just in 2 weeks - and, only 500 of them have been searched for more than 4 times. Truly a long tail.