Fake IP

[iago]

Use the postal service analogy. If I write the wrong return address on a letter, any responses to said letter will be sent to that address rather than my own. Unless whoever receives mail at that address knows to forward that mail to me, I will never get it. That is, in essence, what connecting via a proxy accomplishes.

I already used that analogy in this thread, but you extended it a bit

[iago]

I was thinking, he (or whoever) might be thinking that the internet is like the phonelines and caller id.  Caller id is (optionally) sent from the outgoing phone, and a switched 2-way connection is automatically established without using the caller id info.  Which makes it easy to spoof caller id.  But on the Internet, you need to send your ip to the other person so they know where to send data back to, because you never get a direct line.