We definitely agree you should have only one FB Page if all the sites are related around the same topic.
Regarding your questions, I think there's a few things to clarify. First, Like buttons on pages of your site generally will be for that page or your main domain (
site.com). The like button at the top of all of our pages right now is placed there using the JFBCLike module with a URL set for
www.sourcecoast.com/. That way, when the Like is clicked on any page of our site, our home page is liked. You can leave the URL off and then the Like button would be for the current page being viewed.
The JFBCFan module is meant for Facebook Pages. It can show the latest news feed, show others who Like it, and has it's own Like button as well. I think this is what you're looking for, and it can easily be used across all your sites.
Regarding applications, you will need one for each site if they each will be doing user registration and logins. That's because Facebook requires a specific domain to be set for each application, and logins can only occur to that domain.
Finally, for Canvas apps or Facebook Pages, you can use one of your applications/sites to serve the content for either of these or you can have 4 separate Canvas pages, if you want (like you said though, it spreads things out). With our next release (now called 3.4) coming out later today or tomorrow, we'll be adding a lot more support for Page Tabs and Canvas. With it, you'll be able to set a different template to show when your site is viewed on Facebook vs your normal site. Also, you'll be able to create Reveal Pages which help push people into Like'ing your page. You can see an example of the Page Tab and Canvas apps below. Both are loaded from
wwww.sourcecoast.com/jfbconnect/ and are using the new release
www.facebook.com/SourceCoast
apps.facebook.com/joomla-extensions/
Hope that helps explain, but if you have other questions, just let us know!
Possible to have multiple websites integrated into one Facebook Page?
