Remember though - Slashdot got big in late August/September/October of '98 and continued into '99. The actual date I started reading was August 6, 1998. The Linux explosion happened shortly thereafter, and that's when everyone started joining. I think it's pretty hard to gauge what my UID would likely have been without first finding someone that registered in early August of that year.
Tony - when did you join Slashdot?