Guess something like that is exactly what some Spamthreads are using and i am not a friend of it !
Why need a auto reply script ? To lazy for write or to look after threads and post you have written ?
This is not meant to be used for spam, and there are certainly many useful applications. Threads will only be bumped if they have not been replied to within 24 hours (following forum policy). Lots of us don't have the time to bump all our threads which is somewhat required to keep up with the rest of the forum.