interesting. bootleg merchandise will always exist, i think it's the band's problem how they decide to face it, and that should guide their fan's actions on it.
i mean, for example when a band (i think it was brujeria) was playing in my city they ran into the millions of bootleg tshirts stickers and such merchandise people were selling outside the venue. So they confiscated everything and gave it away to their fans for free during the show. I think that's a pretty clear stance as to what they think about illegal merch.
on the other hand, another pretty big band I know was thrilled when they saw all the bootleg stuff of them, and actually went ahead and bought some cups etc for themselves, saying it was better done than the original merchandise is.
in other words... well, i prefer original stuff to the bootlegs, even if bootlegs are cheaper. if bands don't bring their own tshirts to sell at concerts though, i'll buy one of the bootleg ones. if I knew my favourite band had a problem with it, i'd definitely think it twice. if they shrug it off knowing there's not much they can do about it really, well...