@King:
But in order to monitor meetings, they have to monitor them beforehand. Or else, they wouldn't know about the meetings in advance.
According to Sengoku, they have patrol ships that report when pirates are on the move. This his how they knew various pirate crews along with Whitebeard were on the move. Whitebeard, however, easily dispatched of the 23 ships they had observing him. They were then unable to receive any more information on their whereabouts or their motives. The ships they had observing the other pirate crews were also lost as well. This proves that any Yonko can remove themselves from the sight of the marines quite easily, whenever they so choose to. It's impossible for the marines to constantly keep tabs on them.
Momonga himself states that they have a central that deals with that sort of stuff.
He didn't. That was a mistranslation. They received that information from marine headquarters and it was the fodder marine who relayed that.
–- Update From New Post Merge ---
What do you mean with this? Being a Revolutionary is not exactly a good thing in the OP world, especially from the perspective of Marines and even Doula. They're criminals to the world.
They're not viewed as criminals to all the world as far as we know. The marines are the ones who branded them criminals since they're a threat to them. The revolutionaries actively help people and only attack the marines. According to Robin, numerous countries agree with their ideals. I don't recall Doflamingo harbouring any particular feelings towards the revos. He doesn't even like the WG. @RobZilla:
I doubt being fully integrated as a BB crew member quite fits into the category of "nasty rumour".
All he said was that he hadn't heard good things about him. He didn't refer to the things he heard as "nasty" in particular.
–- Update From New Post Merge ---
You've seen the stuff Blackbeard has pulled, right?
The WG have done worse. Doflamingo knows this to be true. I doubt even he'd question the content of his character from merely being an affiliate of him. Come to thing of it, what has Blackbeard really done in particular that makes him worse than other pirates? All we've seen him do is stuff that regular pirates do on a daily basis. Pillaging villages, thwarting marines, and conquering territories?
That doesn't make much sense.
According to Law, The major players have lain low and didn't make any moves. It would make sense that everything about them isn't open information. A situation where you know there are 10 captains, but not don't know the true identity of the 10th captain could easily occur in various ways.
The marines have no say in working with the warlords
Yet they can easily revoke their status? The system can be removed in the Reverie.