@Jinbei:
I really hate these World Power chats, but I would like to toss a few points out there from the top of my head, for the camp of posters who think Marines + Shichibukais equal the Yonkou. How can that be when it was already stated in the Manga that the Marine Headquarters and the Shichibukais don't get along with each other. Heres the quote Mihawk was the one who said it.
Mihawk: "Marine Headquarters" and "Seven Armed Seas"… two conflicting groups of equal powerholding a "round table" is a meaningless thing.
http://www.mangascreener.com/stephen/onepiece/chapter234.txt
Conflicting groups doesn't mean that they are fighting each other. As a matter of fact both are to a degree on the WG's side. While the Marines work for them WG's as military force the Shichibukai do it as acknowledge pirates. The Shichibukai are supposed to take down other pirates and give a fix percentage of their plunder to the WG. Of course this conflicts with the military force's job as law enforcement branch since criminals are doing their job now. That two groups are in a conflict does not mean that they can't be working for the same guys.
Now for those who are using what Grap said, I would like you guys to reread the quote again, Grap never said the Marine Headquarters must make a team with the Shichibukais to hold off the Yonkou. If that was true there would not be 3 World Powers but two, Since the Marine Headquarters can't stand on its own two feet and need the help of the Shichibukais and Shichibukais in vice versa.
The important factor here is that the whole balance of the three thing is the WG's idea. And from their point of view there's only those who are with them and those who are not. So yes, while it is three powers in terms of three groups there actually just two sides to chose. So yes, with Yonkoh against the WG and the Marine HQ + Shichibukai siding with the WG, you'd have three powers but just two sides.
I didn't see the Marines Headquarters backing up Mihawk when he went to go see Shanks. I didn't see anyone mention Marines Headquarters when it was stated that Moria (1 Shichibukai) was once on the same level of Kaido of the Four Emperors.
Why should the Marine HQ have to backup Mihawk? He simply went to him to chit chat not to fight. As far as Moria is concerned, apparently he suffered a crushing defeat seeing how much his experience at the New World traumatized (sp?) him. Besides that they once were on the same level doesn't mean that they still are. It's not just the protagonists that grow.
Last time I checked it was Shanks talking about A Pirate who is now a Shichibukai, who scared him to a Yonkou Whitebeard.I don't think Blackbeard needed the power of the Marines Headquarters, to scar Shanks who is a Yonkou.
Blackbeard is in the making of becoming the main antagonist of One Piece. Of course he doesn't require help from Marine HQ. The sole purpose of Shanks' conversation was to explain how much of a threat he really is. Kuma's statements support that. And Blackbeard himself said he aimed for the top. He's "only" a Shichibukai because it fits with his plan. Not because he is not on Yonkoh level.
We have yet to see the 3 Admirals which is the Marines Headquarters strongest fighting force, being back up by anyone from the Shichibukais. Seeing how the Meeting went The whole Marines Headquarters + Shichibukai = Yonkou is bogus.
Again, I didn't say that the Marines and the Shichibukai are friends like Spongebob and Patrick. I only said that they are on the same side, at least from the WG's point of view. Remember Crocodiles words "they believe in the Shichibukai". It's true that the Shichibukai follow their own goals, but they are still acknowledged by the WG, which means that on the surface they are on their side. It wouldn't make sense for the WG to form a group if they don't benefit from it. The entire balance of the three powers has to be considered from the WG's point of view since it is their baby. And from that point of view Shichibukai and Marine HQ are on the same side. That the Marines and Shichibukai don't like each other is out of question and I never argued that point.