It's all a gamble. I have been ripped off a couple of times.

If you are not sure, then don't pull the trigger on the trade. I only am willing to trade with people whom I am confident that they get their autographs IP and are reliable. I generally won't trade for something that was obtained TTM or was bought.

Part of the secret to the joy of this hobby is to be happy with what you have. Don't start obsessing over who you don't have. Sooner or later an opportunity will usually come around to get some big name autographs, if you are willing to do your research.

then its the good old creek without the good old paddle!

Check their feedback? That is the only safeguard.

Is it safe to trade autographs with person whom I don't even know his face?
I mean, what if the person gets mine and doesn't send his? Even if the person said it's an authentic real one, what if it turns out to be fake after I get it?