Hi Perry,
"Now he reveals himself privately once someone decides to believe. Do you blame him?"
A general observation can be made on this point. The more distant the account of God's dealing is from the audience the larger in scope the action tends to be (not always of course). Thus in the NT miracles happen only in a small area with just a few people around, or even just one. But in the OT, while this is sometimes reported (see 1 Samuel 3 where God speaks to Samuel regarding Eli), there are much larger settings for some of the accounts, including of course a world-wide flood, separating the waters of the Red Sea, etc.
If however, someone reports being alone and hearing a voice, there is no reason we are compelled to believe it is anything other than what is going on in the mind of the person who had the experience. Of course if God chose to communicate something he would know that would be impossible for the subject to know, such as the winning numbers for the next 10 state lotteries, then we may need to conclude something different.
Cheers,
-Randy