@theinvisibleworm:
It's that and the fact that he accepted himself into the crew easier than anyone else by far that makes me doubt him completely. For all we know one of the Shichibukai or Yonkou roam this area and that's why no ships make it through, and this is his method.
I'm with theinvisibleworm on this : even though Luffy doesn't seem too frightened by Brooke – and Luffy's instinct is usually correct about people -- there's just too much here (the storm, the offering to God that's been ""defiled", Brooke's inability to say "no", and so on) that leads me to believe we've met our new enemy. So even though he'll be a lot of fun for a while and firendly for a while -- Brooke will eventually show us his true intentions.
Brooke may be at the entryway to "New World" in the same way that Baroque Works were at Whiskey Peak and Smoker was at Loguetown (if your goal is to sink as many pirates as possible, where better place to station yourself than at the entry to the next segment of Grand Line? [This could even be how Crocodile got the idea for placing Baroque at Whiskey Peak – after encountering Brooke himself, or hearing stories about Brooke through the other pirates who'd survived a run-in].
Brooke is probably also the key (excuse the pun) for getting through the Florian triangle without harm, so their adventures with him won't be a complete loss ; they'll get through, but they'll have to find some way to chase him off either just before, or just after they do.
So no. Brooke's design is fun and all – but I don't want another super-skinny, skirt-chasing, joke-making pirate on Sunny. We already have one -- and, unlike Brooke -- he's a first-rate cook too.