This is a particular hot-button issue for me, to the extent that at a recent US con I attended, I scratched out "Pro" on my name badge and wrote "Guest." (They give free memberships to their programme participants.) I remember one con where someone came up to me after a panel and said "I really enjoyed you on that panel. Could you tell me what books you've written so I can look for them in the dealers room?" She was totally astounded when I said that I was a fan, not a writer, because she had just assumed that only writers could participate in programming.