Take your top 50 artists. For each of these artists, collect the top 20 similar artists (where the artist itself is the #1 most similar). The resulting number of unique artists is your super-eclectic score. You can compute your own score at http://anthony.liekens.net/pub/scripts/last.fm/supereclectic.php
My super-eclectic score is currently
750/1000
The most similar artists for my profile are Pearl Jam (7), Mark Lanegan (6), Foo Fighters (6), Queens of the Stone Age (6), Soundgarden (5), Wolfmother (5), Audioslave (5), Them Crooked Vultures (5), U2 (5), Eric Clapton (5)