Here's few of "those instances"
As you can see, it's always them approaching him/his entourage in the worst possible time. Arrivals to venues, airports, restaurants or whatever. From the perspective of an artist this is quite disrespectful.
'He refused to sign Iron Maiden albums' = he refused to add significant value to mint condition vinyl that 'fan' would put on ebay afterwards.
I'm not fandom kind of a person but I guess if I were I'd cherish the moment of signing more than the signature itself. From that point I presume these people are not fans but going for the easy money or exposure for themselves.