Is $1000 in rent necessary to cash flow long-term?

[Julia Rowling]

There has been some heated debate in the forums and blogs recently regarding the infamous "$30K pigs." The argument, as best as I can ascertain, seems to boil down to whether it's possible to cash flow, long-term, on a SFR that doesn't pull in at least $1000/mo due to CapX. Is this true? Fellow BPers, please weigh in with your experiences.

Thanks to all for your input!