I saw on Maggie Stiefvater's Twitter (she is the author of The Wolves of Mercy Falls which include Shiver and Linger so far) that she made facebook pages for the main characters in her books. I am not sure if this will help with character development or be a giant waste of time. On the surface, facebook looks like a place to act as a giant advertisement (on the info page at least). Does it really matter what is a character's favorite bands or movies? Sure things like who they are in a relationship with or their religious/political views are important but that usually comes through in a story. However, I think there may be some advantages to making facebook pages for characters.
I think this may work in two stages of character development: newer characters and the stand-alone novel that begins to demand a sequel or even more. For new ones I think the reasoning is obvious. Sure, it's only a list of TV shows they watch, but what if they watch none, they don't have time, they could watch soap-operas, all the geeky TV shows (like me :D), etc... all of these things would help develop a character. Do they play video games? Do they read classics or romances? Though it looks basic and trivial on the surface it could help give characters more depth or more rounded personalities. Also, I have already finished a novel. I am not going to make facebooks for those characters. However, sequel ideas keep coming up. If I were to write another book, I would expand the universe, introduce new characters, and bring some minor characters to more important roles. If that were the case I would make them facebooks.
One other possible benefit. Say this is dream world and the book is published. How cool would it be to promote the book through those characters. They could add fans as friends (given the book does not reach the level of success Twilight or Harry Potter has). More over, fans could find more information about those characters that are not said in the books because they are small trivial things such as bands one likes. I know that there are characters in many movies/TV shows/novels who I would add as friends to interact with them (I am sounding more lame by the minute lol) and learn all those small things such as their favorite sports teams.
If this ends up helping I'll talk about is more. Lets hope this helps.