Why would rogue spiders obey robots.txt?

[irock]

Hmm...

I just checked out Webmasterworld's robots.txt, and it would seem there are plenty of rogue spiders trying to duplicate sites or whatever... so, i was wondering if these spiders are just sent out by unethical people, why would they obey the rules in robots.txt.

Thanks.

EDIT: Oops... I posted it on the wrong forum...

[hakre]

yes that's true. on the other hand it would be a real news if google would do... :)