Piracy was available for the DS and Wii fairly early on but that didn't stop them from becoming the second best and sixth best selling consoles ever respectively. While piracy was one of the factors for the Dreamcast's failure was piracy, it was no where near the main factor.I didn't see anyone say that piracy was the main reason for failure.
But piracy obviously doesn't help. No developer or publisher looks at a console and says, "Hey, this thing is cracked wide open so we should definitely port our games over to it."
The Xbox 360 and PS3 were well supported, but who can say whether or not they wouldn't have been *better supported* if the piracy didn't exist?
It's well established that piracy was certainly one of the factors behind the failure of the Dreamcast. So only a total idiot would conclude that it wouldn't be possible for piracy to have a detrimental effect on any other consoles.
But having said all that, I'm not here to preach. I like free games just as much as everyone else. But let's not bullshit here - piracy is NOT helpful to any platform.