Well maybe my guess is totally wrong but I think that the One Piece treasure is far more then just gold. I think that must be some kind of information that could affect the entire way of living in the (One Piece) world. It´s actually a little longer theory but heck here it goes.
First unlike in every other Pirate story Gold Roger doesn´t want his treasure to be found. In fact he is openly inviting everybody to go and get it. The fact that he was laughing before his death also gives me the impression that he´s actually poking fun of everyone who thinks that One Piece may be gold or gems.
Then there´s Dragon who rescues Luffy so that he can fulfill his dream which would be to find One Piece and become the Pirate King. OK now we all know that the World Government recognizes Dragon as a very serious threat. We don´t know the specifics yet but he is been labeled as a revolutionary (sp?).
Furthermore he was helping Luffy against Smoker in Loguetown. And when he appeared he said something like: "The world is waiting for our response/answer". (sorry I don´t know the exact quote but in the german Manga and Anime he said the same thing so I guess that´s no translation mistake).
So this means that Dragon is very interested that Luffy finds the One Piece and I´m sure that they have something to do with his revolutionary plans.
Then there´s Nico Robin who I think is a very important person here (I guess that´s the reason why we didn´t see a Robin Flashback yet). Let´s see, Nico Robin is a member of a archeologist family, she´s seeking for the true history text and is wanted by the World Government since she was 8 years old.
This is just my personal speculation but could it be that her family already wanted to find out about the true history? And maybe this true history is something that the World Government never wants anybody in the world to find out about. Maybe Robin´s parents were killed due to some World Government conspiracy to keep this a secret. And Robin´s dream is to fulfill what her parents weren´t able to do before their death. This would at least explain why she hates the World Government so much. And there´s also that one anime ending in which we see her as a child where she´s looking sad and angry at the children with their parents. It could be a hint from Oda, but it mustn´t.
Before I mention the next thought I have to make a:
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- S P O I L E R - W A R N I N G * * *
At least for those guys who didn´t read the Skypia arc yet. 
Now when Nico Robin finds the Porneglyph (sp?) on Skypia she reads Gold Roger´s message there. With this message she realizes that the Rioporneglyph (sp) must be a combination of the texts of the other´s she has read so far. But what´s even more fascinating then this knowledge is the fact that Gold Roger found this information so important that he left the huge Golden Bell behind. If the One Piece would be a treasure of Gold then why should he leave the bell and the city of gold behind? I pretty much doubt that at this early stage of his adventure Gol D. Roger was something like:"A now leave this bell and the golden city behind mates! I´m sure that on our journey on the Grand Line we will find a lot more gold then that."
I mean if he was just after gold then he would have taken it now would he? But he didn´t. He left the bell right where he found it and just wrote the message down that he will tell everybody about what he has found out.
Of course everything I´ve just mentioned is highly speculative I do believe that Gold Roger, the One Piece, Dragon, the Rioporneglyph and Nico Robins past and dream somehow are all tied together. But I don´t have any idea what that might be. It´s just another fanboy theory.
Take care
s really not much reasoning behind that speculation, other than the fact that some guns are ‘one pieceâ€
At least in subs I've seen with the first opening, Roger always says that he left his treasure right there. I always get this image that his treasure is right by the execution platform and Smoker picked it up at some point. :lol:
