When we announced the pricing for our 2 link building seminars (London and New Orleans) we included a discounted price for all SEOmoz pro members. SEOmoz, and their members have been incredibly good to Distilled and we want to repay them whenever we can.
The discount code meant that SEOmoz Pro Members got a £100 saving for the London seminar (£299 instead of £399), and a $150 saving for our New Orleans seminar ($450 instead of $600).
After we had launched the prices SEOmoz launched a promotion to win lifetime pro membership (now ended) and started offering a free trial of their awesome software. Anyone, can signup and get a free month of membership, which includes access to the discount code for our seminars.