I think it depends on the nature of the evidence. If the person had significant knowledge imparted to them that would be extremely unlikely for them to know any other way, then that would be far more interesting.
Imagine if a prophet included a page of maths leading up to e=m*c*c or the chemical formula of a cancer cure (although I don't see why a god would invent cancer and then want the cure to be known) or maybe even a work of art that is so inspirational that people are struck with awe? However, if a god wanted to be widely known, it'd be easy to write commandments into the side of a mountain or even create a new bird species whose songs were the different commandments.
The problem with a human testifying about contact with a god is that they should have extraordinary evidence. Third hand reports of turning water into wine or walking on water are too easy to be faked when specific knowledge of the future cannot be faked (unless it's retroactively).
If I ever meet a god, I'm gonna take a bunch of photos, get him to post on my facebook and ask him some specific questions. If he doesn't want to impart knowledge (apart from wishy-washy "be good to others"), then I'm going to suspect that he's a hallucination. There's a lot more evidence throughout history that humans easily hallucinate and make up shit.